In the current WIP chapter of my most popular web serial, there is a scene at the beginning that is presented as happening "now" (that is, having regular story focus) only to be suddenly interrupted by an objection from a character outside the scene, revealing immediately that the actual focus is on the scene of a retelling of the previous scene from one character to another. The transition as it stands is like this:
“No that’s… it’s different when it’s a servant, Eleanor, you know that. That’s hardly the level we’re talking about now. And might I remind you that by your own admission you got extremely lucky even in that case that the, uh… boy has taken to it so well.”
“If you’d just trust in my abilities—”
“It’s not a matter of trust, Eleanor!” Lord Ashwater cried exasperatedly, grabbing his wife by the upper ar—
“Hang on.” Sam said through a mouthful of carrot. “You said you was outside the door listening. How do you know he grabbed her?”
“Door was ajar, wasn’t it?” Catherine gesticulated with her fork. “I could see their shadows on the wall when they got near the window. Now do you wanner hear this or not?”
This gets the idea across inelegantly but with minimal formatting and the only real signal as to the change being an otherwise nonsensical em-dash in non-dialogue text I worry that it will read as confusing and might prompt the casual reader to lose interest and the concerted one to break their flow to go back and examine the transition to understand it. I don't want either of those, but I also still want the transition to be a surprise- so I can't really do something like putting the entire first scene in italics or some other indicator of distance because by convention for flashbacks etc that will signal too early that the scene isn't happening in real time. I also can't do this to the second scene, because then there is no real indication as to when this convention should stop, and I risk ending up with the entire "present" of one chapter of the story formatted completely differently from the "present" of every other chapter.
When seen in film and television, the specific framing I'm trying to evoke is that where "Scene 1" freeze frames in motion, a character's voiceover plays over the frozen frame voicing an objection, and then the camera hard cuts to the other character in "Scene 2" replying, often with set dressing and shot framing that quickly get the audience up to speed with "Scene 2".
I am limited to formatting within the intersection of powers of bbcode, markdown and rich text and as this story is a serial release I cannot go back and change the formatting of any previous chapters to enable new more radical formatting conventions.