Allow part removal from symmetry groups

[Plibbert]

Currently you cant remove parts from symmetry groups. So if you place 6 radial decouplers, they will stay as a group of six, you can split them between stages. 

 

This is just a really nice QoL Update I would hope to see before we start getting large content packages. It makes building large ships a lot easier.

[Skystorm]

I agree, and this was a feature we had with KSP1 removing from symmetry.  Also, having more/higher symmetry options beyond 8x would be great as well.

[whatsEJstandfor]

Thirded. As it stands, doing asparagus staging is highly manual (needing to pause when fuel in one set of radial engines runs out, then finding the correct decouplers, then decoupling them, then unpausing).