Unless I’m not following what you are trying to do, you should be able to do this. Corkboards are a way of viewing the child items (those items in the binder that are indented beneath it), and so this can be applied to anything in the binder, since all items of any type can contain other items.
Abstract knowledge aside, the easiest way to do what you want is to either double-click on the card’s type icon next to the title or press Opt-Cmd-O to open it. When you first do this, you’ll get a standard text editor, but you can jump back to Corkboard mode with Cmd-2, or by clicking the icon in the toolbar. The corkboard will be empty, because this particular item does not yet have children, but from here you can go on amplifying the main topic with sub-cards just as you would on any other corkboard. This principle can be taken indefinitely. All of the cards on this sub-board can each be opened and have their own corkboards assembled, too.
If you like working this way, you might want to consider turning on the Navigation preference option, “Treat all documents with subdocuments as folders”. This way, you won’t have to keep switching to Corkboard view mode when jumping up or down the hierarchy.
Just think of Corkboards as being a bit like an electron microscope. You can only view one layer at a time, so to switch to seeing something higher or lower than that layer, you can traverse up or down the hierarchy in the binder. Bear in mind that when you add sub-cards, you are actually breaking apart the topic into smaller pieces. Working this way, you’ll probably want to familiarise yourself with the Scrivenings view feature, so you can view an entire topic as one file, even if it is comprised of dozens of cards beneath it. This level of separation can be easily hidden when you compile, so the reader will never be aware of the fact that the page they are reading came from multiple items.
One last tip, if you like shortcuts, you can quickly return to the parent corkboard after you’ve added all of the sub-cards you want with Ctrl-Cmd-R.
I just had to laugh at this analogy. While I actually have used an electron microscope, I would guess that it’s not the first shared cultural touchstone most people reach for.
And really, for layer-by-layer studies, you’d probably need some sort of ion beam. Only that’s destructive, which Scrivener certainly is NOT. 8)
But for the OP, I’d suggest thinking of each card as potentially being the top of a stack related to that script (or part of the script). You can pick up the stack and fan it out, but you can’t see more than one stack at a time.
