How do I bind multiple actions from different categories to the same key?

[eXponentia]

Apologies if this has been asked and answered before, my 15 minutes of searching just turned up things about some update that broke keybindings and how to fix it.

 

Just bought this game, and I want to change the key to sneak from control to z. Simple enough, just want to put the minimap zoom on control, and sneak on z to swap the two. However doing so forces me to remove "Lower Submersible" and one other that I can't remember, and rebind them as well. However I can't rebind them to control, because minimap zoom is on control now. Why are the default bindings capable of doing this, but I'm not?

 

Any help would be greatly appreciated.