Thank you all for your comments and clarification!
With all of this extra time at home, I will be going down the path of Python.

I found this in c4d.BaseObject in the documentation:

import c4d

obj = c4d.BaseObject(c4d.Ocube) # Create new cube
obj.SetRelPos(c4d.Vector(20))   # Set position of cube
doc.InsertObject(obj)           # Insert object in document
c4d.EventAdd()                  # Send global event message

Now to convert 2D mouse coordinates to 3D and input those (on click) to the obj.SetRelPos(c4d.Vector(x))... I know this is an x,y,z vector, as this code generates the cube at 20,20,20. And it looks like the code works with centimetres, not inches, even if my units are in inches. I may need to do some conversion down the road...

Thank you for your reply @r_gigante . I don't fully understand what you are saying. Is it illegal to make this plugin?

Hi everybody!

I am new to developing for C4D and programming in general, but I've used it for some time modeling and rendering for design work. Usually I'll model in SketchUp (for accurate scale and measurements) and import to C4D to render. However, I've started modeling a lot more using C4D because it's just faster to skip the export/import steps. I've been using Primitive Sketch 1.0, but I'd really benefit from 2.0. Unfortunately, I can't find it anywhere, and Carter Cross (original developer) isn't replying. Should I try to re-create this on my own? What do you recommend?

Thank you!

Edit: here's a video showing 2.0