That thing, right there!jsc wrote:"this flat part abuts that flat part"
So, with one of those modelers, you'd be able to anchor a modifier mesh to the thing it should modify, perhaps with an XYZ offset and an ABC rotation. Then they'd stay together as you fiddle with the model and you could move / rotate the mesh relative to its anchor, all without eyeballometrically nudging stuff with a mouse.
Basically, OpenSCAD's parameterization, minus the torrent of equations, plus a GUI interface...
I'm not qualified to carry his water bottle...nophead has done similar things with OpenSCAD