This is a replacement for the really bad clothes-clip like magnetic thing that Molex provides with their "0640160205 Hand Crimper Tool Rectangular Contacts, 18-30 AWG Side Entry, Ratchet" to hold the crimp connector while crimping. The crimper is really good, the magnetic adapter - meh.

So, this is a two-part device printout. The little piece slides into the large piece which is then screwed on where the old clothes-clip magnetic shelf went.

When done, there's a rectangular hole of the right depth so you can just place the crimp connector into the hole, then crimp, then remove the crimped wire. Painless.

Note that I used a 50% infill to get strength up on this thing. May not be necessary, but...