To answer, if only rhetorically, unfortunately as far as additional materials on figured bass syntax go, I seem to know what you know. There definitely could be more out there, but most of my understanding of the tool comes from brute force trial and error (that combined with the fact that I happen to have written at least one contemporary piece for baroque orchestra and included figures, some of which were… advanced). But also, in glancing at Ben’s tutorial, I also can’t say I know too much more than what he’s got there, at least as far as popover syntax goes.
I will say that one of the devs did show me a pretty neat trick regarding suspension chains in this thread here though: The Future of Figured Bass - #9 by claude_g_lapalme
But beyond that, hard to say what else is out there.