I'm trying to mask a material using multiple mat IDs.
I can get into the Mask ID Editor and select a single ID, but I see no way to add additional IDs to that material. There is no add button and I've tried various shift/ctrl combinations but nothing seems to work. The only other option in the window is Add general category which doesn't seem to be what I want.
The documentation says this is possible, but doesn't explain how to actually link multiple IDs to a material...