For fillets / chamfers of simple objects I've been using BOSL2: https://github.com/revarbat/BOSL2 https://github.com/revarbat/BOSL2 They come with fillet / ch

For fillets / chamfers of simple objects I've been using BOSL2: https://github.com/revarbat/BOSL2 https://github.com/revarbat/BOSL2 They come with fillet / chamfer masks, but in general I've been just using their cylinder / cube replacements that generate rounded intenral corners, and just diff'ing them out of existing shapes. In general, I've gotten a long way by just starting with chamfered/filleted shapes (the library includes a neat way of specifying which edges of the shapes you want filleted), and using the intersection / difference of filleted cubes, cones, and cylinders. Intersections on curved surfaces seem impossible any way of looking at it (minus some projection nonsense, but that's expensive in openscad)