you can also sketch on faces sketch(extrusion.endFace(), ...) which will extract the plane from face and put the starting point on the center for convinience.
Inspired by yes, it was one of the ones I tried. I like your approach to selection eg endFace, intuitive selection is definitely one of the trickier parts of a code based approach.
The user can create planes with plane() command e.g plane("xy") or plane("xy", { offset: 10 }); but I have added some shortcuts for common planes (https://fluidcad.io/docs/guides/sketching/introduction#sketc...)
you can also sketch on faces sketch(extrusion.endFace(), ...) which will extract the plane from face and put the starting point on the center for convinience.