I have been having trouble isolating what exactly the clickable area for group roles are in the various windows. Talking about the specific element that reveals the context menu entry for group roles.
* Player Window - at first I thought it would be name, hp gauge, or the group role icons but those are every bit as random for whether I get the context menu to show roles as any other part of the player window. Still tight fitting bounding boxes on elements but I know the overlap on them and it hasn't helped narrow it any.
* Group Window - so far it seems to be the whole I stack name, gauge, percent, or no context entry at all. It seems like below-left of the built-in name label might be it but still not getting the menu every time.
* Extended Target Window - think I have this figured out. It seems to be the entire combat role button but only if DecalOffset is not set. If DecalOffset is set then it's only the part of the button that is not the decal. This behavior seems backwards from how you would think it works but it does align with consistently getting the Roles context menu entry.
At this point I took to drawing one of the gauge sets on paper as it's bounding boxes using 1mm = 1px. Helped figure out extended target but hasn't helped with group or player window yet. Though with overlaps all sorted out, I can get it more often when right clicking randomly to find where the menu will appear this time but that's only because every element has plenty of clickable space now with reasonable overlaps. Really doesn't help whether an element allows click-through or not seems very random, some do and some don't.
Edit: I will have to upload the UI somewhere else to link it in it's current state, the folder is 2.7MB as a tar.7z (zip is twice as large). Dropbox link