More than anything, what I _really_ want is an interactive tool which allows me to work in both 2 and 3 dimensions, tagging points/coordinates with names and then referring to them by name while applying distances/lengths and modifications such as arcs and curves.

I've been using Open(Python)SCAD: https://github.com/WillAdams/gcodepreview but have wished for an interactive tool which would allow programmatic usage as well (apparently OnShape does this by having FeatureScript as the basis and the UI simply edits the script?).