Stage productions aren't just about the script.
In your corpse example, there are several ways to handle it and it depends on the director more than the playwright.
The corpses pile up and then there is a marker to indicate the end of the act which resets things. The corpses turn back into actors and get up and walk away.
The character falls over and dies off stage (or falls onstage and crawls off to die). The injury causing the death would be onstage and obvious. Actors left onstage could react to "seeing" the character die, even if the audience can't see them.
Same as above only the final fall-down-and-die is behind a set piece.
Someone drags them off.
This is something I've actually dealt with. In the classical ballet production of The Nutcracker, one of the acts is The Battle Scene where toy soldiers come to life and both they and mice grow to the size of humans and engage in battle. In most versions, both soldiers and mice get stabbed and die on stage. In the production we're involved with, other mice or soldiers drag off their fallen comrades-in-arms. In small productions (like ours), the dancers playing the dead come back on stage as reinforcements. (And trust me where I say that not having the young children doing this rehearse pulling the dead characters all the way off stage before the dancer resurrects leads to some unintended consequences.)
In general though, the director will make changes. In ballets, a double pas de deux will turn into a pas de trois, if you're short a man (as small companies often are). A scene designed for 5 characters might become one for 4, if they're down an actor. Or 6, if they need to fit someone else in.
Your job as a playwright is not to dictate the absolutes, but to make clear which parts are important to keep as is and have flexibility for the rest. To minimize changes, make sure your asks are possible.
The most important thing to keep track of is where your actors are. Don't have a character enter stage right 5 seconds after exiting stage left. Either allow enough time to get around or change the staging (and here I mean, don't write something that requires an actor to come to a particular location that isn't feasible...the director will figure out blocking early on in rehearsals).
This includes keeping track of costume, hair, and makeup changes. While performers can and will change in the wings if they have to, there are still limits on how fast this can happen. For example, if you use the same actor to be a 30 year old and then her/himself at 70, put a transitionary scene between the time jump. The dancers I work with can change costumes in about a minute and a half (in the wings, with help, assume 4-5 pieces per costume), 2.5 minutes if they also have to change shoes. If they have to do anything more to hair and makeup than pull out a hairpiece and stick in another, not only does the time needed increase dramatically, but you have to account for time to and from the dressing room because they will need more light than you can have in the wings.
Other things to keep track of are set pieces and props. If you want to go from a scene at school with 10 actors sitting at desks to a scene in someone's living room, you're going to need at least 3-4 minutes in-between (and frankly, this is better done with an intermission).
I was in a play in high school where the actors who weren't on at this time had to work behind a closed curtain in the dark to make a change of this magnitude. We had 2-3 minutes while a small scene played out in front of the curtain. During dress rehearsal, I found myself still on the raised set platform as the curtain started to open. I rushed, flew off the platform on to the main stage, and ended up in the ER with a (thankfully only) badly sprained wrist (and did my performances in a brace). While this was the director's fault (we'd asked for glow-in-the-dark tape to mark the stairs and/or low-level lighting and didn't get it), there was no reason for the author to have made this transition so fast. A major company has special equipment and moveable sets, but high schools don't.
With props, remember that a prop off stage stage right isn't going to magically appear for an actor to grab stage left. Not all props are easy to duplicate. If you write that an actor drops a prop on stage, unless it's the very end of the act, write in a way to get that prop out of the way. If a prop needs to be swept up (falling snow in the Nutcracker's snow scene), make really sure it's at the end of an act. This is how accidents happen.
If your play requires certain types of staging, state that up front with the cast list. It's okay if you must have flying harnesses, backdrop changes, rear curtain projectors, etc, but make sure no one commits to the play before they realize this. If you can provide alternatives, do it.
There are many more examples but hopefully these are useful.