Latest Glyphs 3 version.
When I rename a glyph, Glyphs does not accept the name that I provide but changes the name to something different altogether without apparent rationale.
to arLam.medi_arAlif.fina I add .bak, hit return and Glyphs names it
arLam_arAlif.medi_._fina.bak
This is probably related to the custom naming scheme, which is a weak spot in the app altogether: features do not get applied as defined in the code, positioning of marks to base characters is off when the glyph name is not specified in the GlyphData.xml. Maybe this could be improved in v4?