I've been doing some fiddling with groups, converting a Vicky item to fit Posette. Looks OK from the front, but... Anyway, you can re-group in the Setup Room, but the process is a bit quirky. You select the group you want to make the polygon a part of. You need to Ctrl-Click on the polygon. Use the ungrouped and multi-grouped functions as a check on the result. Even when the revised grouping is OK, you'll have an extra group. called something like "NO_BONE" which you must delete before you can exit the Setup Room.