@d-healey Turns out you were kinda right and I had done something stupid.
When I changed the preset browser from 3 to 2 columns I just left the default widths as 3 x 0.33333
It didn't seem to matter as it worked fine in HISE but in a built plugin it was doing what I described in my OP.
After your suggestion I flicked it back to 3 columns, re-exported and sure enough the factory presets weren't editable & the add buttons were there as they should be.
I then changed it back to 2 columns but set the widths to 2 x 0.5 and when I re-exported it this time it was also working correctly.
Glad I have that sorted as it was really bugging me. Thanks for the assist
