I have a round corners filter on export, but it appears that it works on the glyph and the _subtract glyph before they are combined, not after, so I have sharp corners where the subtracted elements knock out of the letter. (I have the subtractor filter set to “mask”, as I need it to be non-destructive). How do I get the round corner filter to apply after the subtraction?
You mean you have some shapes that have a “mask” bit set and you like them to be rounded, too? Have you tried a “PreFilter”?