Variable Font Variation Glyphs

When I use variable code in a rlig feature such as the following:

condition 85 < wght <  90, 100 < wdth < 120;
sub e by e.round;

The glyphs that use e as a component, i.e. edieresis doesn’t swap the e for the e.round. Does this feature not take care of component glyphs in one go, i.e. do I have to manually make alternates for all the glyphs that use the glyph being swapped out as a component?

Ok inspecting a GXTTF produced by GA3 that had alternate layers tells me in fact you do need to make all those alternates.

Yes. With brace layers, Glyphs will add the alternates for all composites. When you do it manually, you need to add those, too.