Exporting Glyphs Filters with glyphs2ufo

I’m using fontmake to compile fonts from a glyphs file that has the **RoundCorner** filter applied to it’s instances. Is there a way to have glyphs2ufo preserve that filter?

Start at the glyphs2ufo export path and trace how instance filters are handled, using the RoundCorner filter and fontmake workflow described in the issue as the example. Determine where filter preservation is lost; done means a Glyphs file with RoundCorner applied to instances retains that filter through glyphs2ufo and remains usable by fontmake.

Written by the indexing model from the issue text.