Slant filter on export

I have set a filter that does a Slant transformation on export (TTF). Is there a way not to apply it to composites? The composites are slanted twice, because the base glyphs are already slanted. It’s not a problem when exporting OTF, because composite glyphs are decomposed there.

The Transform filter should be able to do that. Have a look in the help file (the ? in the instance page). It will tell you about the syntax.