When trying to add the script to prefabs and add them to the selection panel they end up being transparent. Checked the logs and can see it Throws a permissions error regarding writing the png files, despite granting all possible perms to Unity and the system authenticated user. Permissions don't actually seem to be it's problem, as i was trying several approaches to see if one would give before i tried pulling apart the code - and it seems when you CONVERT mesh's to Prefabs and THEN import t hem it all works well, so whatever failing we have in the add script phase it's avoided in the full Mesh > Prefab > Scripted > Selection Panel. Unity 2019.2.0b9 (project dedicated to testing this potentially mind blowing tool) :P