I didn’t like Dune3D; its interface is clumsy even if the 3D constraints thing is interesting.

(Which is not to say that I am not pleased to see more open source CAD packages taking different approaches. Dune3D is interesting, Blobfish's Cadseer is very interesting to a coder I'd have thought, and SALOME has obvious value)

The one small tweak I would suggest for FreeCAD is to use the tab bar workbench selector rather than the dropdown version. It’s such a small change but it helps flow between things in a way that feels like the various functions are more closely integrated. That, combined with custom panels if you want them, makes it more fluid.

(I am not making any particular claims for FreeCAD's usability; I do though think it is much better and much more learnable than the average HN perspective of it, which seems to often come across more as TUI-exceptionalism or "but I don't wannnnnaaa learn a guuuuuuuiiii". GUI CAD isn't intrinsically some inferior, imprecise, unformalised thing.)