My vocabulary size right now is ~10000 words and I want my vocabulary to be as big as a professional writer, I want to have the ability to manipulate words. I mean SUPERIOR vocabulary.
Sorry, there's no better way. Read often, read lots, and read stuff you are unfamiliar with and not just things you like. A lot of "superior" vocabulary is really just old-fashioned, so read classics. A big part of a superior vocabulary is understanding context, and if you know why chasing a white whale is important, you've won the respect of anyone who's read Moby Dick. If you are writing about a subject, read reference materials or text books in the subject field.
If you find words you are uncertain of, look them up. Don't just rely on context, but do pay attention to context so you understand HOW the word is used - a definition can be deceptive on proper use.
Read the dictionary:
If you only read one book, that's the one. I know it doesn't exactly read easily, but if you want a great vocabulary, this has the definitions and typically an example sentence to go with it. Day one, you can start discussing absinthe and the defensive use of an abatis. Once you start discussing zooplankton, you're well on your way to a near-offensive vocabulary.
There are several things to unpack in your question.
The first is this, you are very likely to have an effective vocabulary of several times the ~10k words you believe you have. Just from reading your question, I gain a sense that you have an innate grasp of the structure of symbols, and how to apply them in multiple contexts using words. You may not be confident in your ability, and it likely does not yet reach the level of polish you desire, and recognising you have growth to achieve is a good first step. I am saying this not just to blow smoke, but so that you can think more clearly about your actual goal.
Yes, an expansion of your vocabulary is a must if you want to write, but in all honesty, it is not the only thing you will need. It can also be a distraction for your audience if you use a vocabulary far beyond their capacity. Stephen Donaldson uses a Wide-ranging word choice, and not all of it is simply constructed words to fit his created Fantasy world. This does not stop him from being wildly successful, But I'd suspect his success is in spite of this, not because of it.
It is true that a good way to expand your personal vocab is to read, but if that is your first method, then you must apply a technique in your reading, if you will, a method to the madness. Make no mistake, to read, and read widely is a way that can lie a form of madness. It can be a curse beyond imagining. Once you begin, you can hardly ever stop. It is as potent an addiction as heroin, and as unforgiving a master as Mephistopheles. The technique you should apply can be determined by your end goal, to simply expand your knowledge of words you could accomplish much by reading a dictionary. While you might want a good one, to simply expand your breadth of knowledge virtually any will do.
To take your manipulation of symbols in the direction you indicate, reading by authors who challenge you with their own use of the craft is the path to walk with trepidation I allude to above. It is those works themselves that will catch you, and trap you within their spell. Regardless of your preferred genre, you will find it intoxicating to immerse yourself in a book that transports your mind to another realm. That intoxication, will lead you to read until the sun comes up, it will lead into withdrawal if you don't feed the monkey on your back.
Edit:add a bunch of references
There are a lot of different places to get guidance on how to write, while you are asking for guidance on increasing vocabulary, that is truly only one aspect of crafting a narrative that captivates your audience's imagination. There are some writers I respect who have shared how they craft, and I think you could gain a lot by looking into their advice
I have selected these pieces of advice from authors I respect, and whom I personally respect the advice itself
https://en.wikipedia.org/wiki/Aspects_of_the_Novel https://en.wikipedia.org/wiki/On_Writing:_A_Memoir_of_the_Craft https://en.wikipedia.org/wiki/Zen_in_the_Art_of_Writing https://www.ursulakleguin.com/steering-the-craft https://www.amazon.com/How-Write-Best-Selling-Fiction/dp/089879045X https://www.masterclass.com/articles/neil-gaiman-quotes-on-writing#neil-gaiman-quotes-on-writing
I would expect the best place to get most of these writers books and many other resources as well as a wealth of reading material that will expand your horizons and vocabulary is your local library
The second thing to unpack, is there appears to be an assumption that a larger vocabulary will naturally lead to a greater ability to manipulate those words, to stretch someone's ideas in different directions. I'm not so sure this is a direct line. You will need to work at putting meaning into the structure of your writing, this takes practice, but more than that, it takes a solid purpose, A strategy to what you write. It is something that some authors have innately, and some authors need to work at, and some authors just don't use that entire structure of subverting meaning. This last group of authors simply tell a beautiful story that can be equally engaging.
The third thing to unpack, is this - the most important part of learning to write, is writing. Find a place where you can receive feedback on what you write, and try out some different styles. You may want to start with short-form, investing an entire novel's effort to elicit your first feedback could be problematic. There are places online to get this kind of feedback, but if you go down that route, don't post your most exciting ideas that you want to use as the kernel for your real writing, come up with something small, and divergent from your eventual direction.
I looked at the results of a test by the Economist and they say a native speaking adult has a vocabulary of between 20,000 and 35,000. An eight-year-old has a vocabulary of 10,000.
Why am I telling you this? A child's vocabulary is largely transactional: I want something and these are the words I need.
To expand your vocabulary, you need to move beyond everyday usage and beyond what is functional.
Now you need to make a choice: do you want British English or American English? (I know there are other variants but these two dominate.)
It will help if you decide whether you want to focus on fiction or non-fiction because the vocabulary of each differs significantly.
Read contemporary texts that are well written. (Classic texts are okay but the meaning of many words has changed significantly.) When you come across a word you don't know, guess what it means. Use the context to make a stab at it. Then check the meaning in a reliable dictionary. Write down the word and write (or type) the meaning. Don't copy and paste it because you won't remember it. Make a list. Every so often, read over the list. (Try covering the meaning and seeing if you can remember before viewing it.)
What takes time is discovering the connotations of words and these are often not given in dictionaries. Guessing what a word means before you look it up will at least give you a feel for whether it is positive or negative.
At the end of my secondary school teaching career, there was this big move to expand students' vocabularies by making them learn words and their meanings. Great. Except that they didn't know how to use the words correctly and they didn't know their connotations. It was ultimately pointless. Getting students to read more widely and think about words they didn't know was more effective.
Write a sentence...
Add an additive you know, and then search for 'Other words like'.
I do it, when describing things.
It is not just a beautiful morning. It is a ....
attractive pretty handsome good-looking nice-looking pleasing alluring prepossessing as pretty as a picture lovely charming delightful
Some of them miss the mark, but You can find some that works.
After each time, write the new words down, and read them at night.. and the next morning.
Utilize a thesaurus that includes word arrangement by category. For example, Roget's International Thesaurus, 7th Edition.
You can use any thesaurus to find adjectives (thus expanding your vocabulary of alternatives/similes). However, I find reading a non-categoric thesaurus much like reading a dictionary - it's fine for a specific application, but not particularly good for recreational reading. In contrast, I find reading about words related to a general category to be far more enjoyable.
In addition to reading, you can also use the thesaurus to improve your vocabulary with writing exercises. Take a sentence, use the thesaurus to make a substitution & think/write about how that change impacts the writing. Is the tone different? Does it sound worse? Why?
Finally, I find it helpful to graze a general category when I'm writing about something unfamiliar. In this way it acts somewhat like a glossary and it allows me ask better questions as I can research pertinent terms. Instead of building out my vocabulary one word at a time, it lets me sift through a chunk of content at a single time.
Read, read lots, read lots of different things; Read your favourite genre work, it will help you with technique as well as vocabulary common to such works. Read science related to your preferred genre, it will help you with technical vocabulary, useful for making your own notes, interpreting notes others have written and for writing exposition. Read science not directed related to your genre, you'll be surprised what turns out to be useful. Read dictionaries and thesauruses for general vocabulary just try not to use too many of the obscure terms you find therein or your writing will sound "like you swallowed a thesaurus" this is often off putting to readers.