Breaking group associations between multiple symmetric parts

[Vermil]

One thing I often find myself wanting or needing to do, is to remove just one or a few of parts, which have previously been mounted as symmetric parts of a group.

For instance, I want to modify the way four engine complexes work, i.e. how they are mounted. I want to make two of them different.
Currently, this means I have to tear down everything, fuel distribution lines and tanks, decouplers, radiators, struts, then rebuild everything again as pairs or even single complexes, and then re-organize everything in the staging-queue again.

I want to tear down only two of them.

Is there a method to do this already?  (I'm not the sharpest knife in the drawer, when it comes to figuring out how a game works, I did my first Minmus landing without either SAS or navigation nodes, so call me Captain Clueless.)

But if there isn't a such method, could we please have it?

 

[nikokespprfan]

There is a mod for breaking symmetry: 

But I would support for it to become stock.