A fairly standard thing in programs like Photoshop or Gimp is that a given "brush" can receive a different shape, so you keep all of the parameters of the brush except for that shape. In Painter, that seems to be a matter of the "Captured Dab", but as I understand it, while a brush will retain its captured dab, when making that setting, if one is not assigned, you have to assign it there by capturing a new dab. Is there a way to, say, open up a wax crayon brush and then set the captured dab to a particular standard shape like a square or a star? As I understand it now, you're basically limited to either capturing a new dab (maybe doing a star in Gimp, pasting it over, selecting it, and capturing the dab?) or if you already have it somewhere as a brush, you could take that brush and then start adjusting parameters to that existing dab, then save it as a variant.
nope, that's not something painter can offer, no matter how useful this feature can be. your understanding of painter having no real internal dab library is correct - at best, you can use OS search in the brush library folder and pull .jpg dab files from there to open them in painter over and over.
I love how paintstorm studio has their captured brush nibs organized - you can arrange them in the custom folders and there's a built-in little editor that does dab rotation and flipping on the go, and the application remembers those changes. clip studio paint allows custom tags for every nib sample, which is less convenient but still very nice to have layout and management-wise.
This sounds like a very cool feature - "internal dab library" - would be nice.
I also wish you could capture a dab on a layer.