How do I convert two synced mono tracks to one stereo track?
Or split a stereo track into two mono tracks?

Thx

This isn't possible currently, however I'm looking at options for adding destructive editing.

Not even some weird, clunky workaround involving multiple copy/pastes?

It’s an issue since many available multitracks come in stereo pairs even when (at times) the source was mono.
Or worse, stereo pairs that come as separate L & R mono tracks. Aside from the misleading graphic representation, it’s a real pain to apply the same edits, FX, level, etc to each of two mono tracks always.

Actually, it's easy to go the other way and merge 2 mono tracks to one stereo. Try this:
Align the regions vertically on 2 tracks, and pan one track far left and the other far right. Put the volume faders at zero and with no track FX.
Select both regions, and use the (Hotbox > Bounce) feature, now you should have a stereo mixdown on the pasteboard.
Paste onto a new track.

Okay.
Can I use the same Bounce to change a “stereo” bass track to mono?
There appear to be several like that with a mono instrument duplicated in R and L of a stereo track.
I only need one.

Not currently. There was a way previously, which involved pasting stereo onto a mono track, but now that tracks can share mono/stereo regions we can't force a mono conversion.

I would also love to have a way to bounce tracks to a mono track again. Thanks!

I slightly misread. Never mind.