I have a single axis setup with 3 masters which I’d like to export as a variable font. I need bracket layers in a few glyphs, so all 3 masters need to have compatible special layers. In the example below, if only Regular and Bold have bracket layers the variable font will not switch glyph shapes. If all 3 have bracket layers but the Light one is incompatible there will be an error on export, but Glyphs will NOT flag it as incompatible.
Now, shouldn’t ALL bracket layers show up on Show Master Compatibility and Fix Compatibility? I understand it ignores the layers that do not have any effect on the final interpolation, but I believe this has changed slightly with variable fonts.