hi, i wanted to give a quick update on this! i tried out the temporary workaround i mentioned (trimming down all my separate png parts to remove excess transparency) and re-rigged my model. it definitely helped with placing larger parts, but i found it was still really difficult to work with smaller parts that overlap each other - eyes/mouth/glasses/etc was a pretty rough time.
i also found while working on different emotes that the "unclick" selection (idk what else to call it, but the fact that it will select a nearby piece as soon as i RELEASE the mouse after dragging a different piece into place) will grab pieces that are invisible on the emote you're working on. i don't remember if this happened at all in the video i sent initially -- i don't think so, but i also think i just didn't work on emotes during that session. sorry that i don't have a video this time! i'll just try to explain as best as i can... let's say there's an arm piece that's enabled for emote 2, but not emote 1. while trying to move pieces on emote 1, sometimes the "unclick" would grab that emote 2 arm, even though it's not even visible on the emote 1 layer. (this would also become a mildly annoying issue when i was trying to click away/into blank space on the honk screen just to deselect stuff, and instead i'd end up selecting a hidden piece from a different emote that i didn't realize was there). i figured i'd mention it since it seems like it's potentially related to the overlap issue!
thank you again for all your work on this!