Be able to re-use windows/splits by plugins

We can ask for new windows or split-view panels to be shown from API calls.
But as we use these more, we need some other controls as well. Particularly, to reuse existing splits/windows if open when opening a new split or window. This will stop many windows piling up when calling the same commands in quick succession.

I can think of various potential solutions, but as I don't know the relative complexity of these, I'll restrict myself to giving some more detailed use cases.

SearchExtensions' /quickSearch and /searchOver* commands

These commands open a new split window as a convenience when they run. When you run the command again (or via the psuedo-button at the top of the note), another split window is created, even when there's an existing split showing the same note.
I want a way to say "show note in new split, unless that note is already open in a window, in which case just give it focus".

Reviews' /project lists command

This opens an HTML window. If it's run again, it re-uses the same window -- this is what I want in the first use case above.
But it's easier here, as there's a limit of just 1 HTML window at a time.
When that limit is removed, this also needs a way to say 'reuse'.

NoteHelpers' /open current note new split

To make things slightly harder, this command shows the need to be able to deliberately open a second split view of the same note as is already open in the Editor.