I would really like to see someone work that up.

I suspect that Moment of Inspiration and Rhinoceros 3D are something along those lines, but I'm not aware of an opensource tool which hoes that row.

One thing in particular which it would be nice to see would be a facility where one could draw a piece of geometry, then all the coordinates/values which describe it could be displayed in a pane where they could then be named or re-arranged, or the values changed, or even the values changed into formulae.

That is actually not so bad a reason. I use build123d, but want it in haskell, enough to look at how hard it would be to create something similar.

(I also totally agree about the gui being worth having sometimes, and would have loved the ability to fully mix. Code as the main driver, but gui to help choose it. For example to figure out faces and other attachment stuff)