How to create an independent, mirrored copy? Problem with parent/child relationships.

I modeled something like a robot - a group of geometries, connected with each other through several parent-child relationships.
I need an exact, independent, mirrored copy (so that all these relationships are preserved).

Joining the geometries before mirroring is not an option, because I would loose all possibilities to modify locations of the single entities later on.

If I mirror all the single seperate geometries one by one, I am almost there, but the whole mirrored object then is still connected to the origin-object transformation-wise. (If I change the transformation of the origin-object, it influences the mirrored object, and this is not what I want (what I need is like a copy, completely independent).

Is there a command, that would seperate the origin-object from the mirrored object, so they are completely independent?

Many thanks for your help!!

Object -> Make single user ?

In object mode, Box select [B] entire assembly. Duplicate the whole thing, [Sift] [D], and drag it where you can see it. Now scale this new whole copy, hit [S] and the mirror axis [X]. Key in “–1”. You will get a mirrored exact copy.

Depending on the use, you might need to Apply Scale and Rotation to each new object, [Ctrl] [A].

Thank you!!!