For what it’s worth, this is on my list of things to attack for a future update. But it’s a nasty hunk of work, thanks to decisions made by past Chris around a decade ago: What a goof that guy was! 
In case it helps, here’s my own process:
When I’m working on sections of a phrase, I tend to use the transcription cursor extensively to break things up when I’m trying to first wrap my fingers around something. (I have some more on that part of the process here.) I’ll toss a region around the chunk that I need to work on, and then work until I’ve got that part down.
At that point, I usually delete the region: I discard them because they’re so easy to create.
Only when I’ve got the sections worked out individually do I start making gradually larger and larger regions. Some exist only to tie together tricky parts of adjacent phrases that I have trouble moving between, so I can drill myself a bit more.
But I can totally see why you’d want to keep a few of these “drills” handy, which is why I’m keen to add this ability to save a set of regions that could overlap.