Can an external projection's reference be deleted to make it a "normal" line?

I have a STEP file that I want to redesign in FreeCAD and make it parametric. I am using the External Projection tool and then drawing multiple sketches and performing pads, pockets, etc. to get it to match the original STEP perfectly. Once done, I don't want the imported body or its projections anymore, and have an independent sketch instead.

Is there some way to "detach" the references (either in the UI or via a script) so I can then add constraints? This might be a workflow problem, I don't know.