I’m working on an complex typeface and I need the glyphs to be ordered in different groups not showing on the sidebar, like the Corners, Brushes or Segments groups. Is it possible to do multiple groups like this it for a single .glyphs file ?
Yes, the easiest way is to make a filter. At the bottom left of the glyph view, you have an option to add a filter where you list glyph names. When viewing in this filter, the glyphs are shown in that order (any unmentioned glyphs do not show up).