GUI for multiple Environments

One can obviously put several EnvirGuis in a Layout, but I’m wondering if there are some more refined (i.e. space saving) ways to do this:

I see I can arbitrarily chain environments (well, IdentityDictionaries), i.e.

~d1 = (x: 1, y: 1, z: 1)
~d2 = (x: 2).parent_(~d1)
~d3 = (y: 3).parent_(~d2)

~d3[\x]; // 2
~d3[\z]; // 1

EnvirGui(~d3) // alas only \y  is shown

But the EnvirGui hides the underlying layers (parents) from me. I guess I could hack that…

Or better perhaps, is there a nested Environment/Event GUI ready made (as a quark)? By nested I mean the usual way this is done is SC e.g. (foo: (x: 1, y: 2), bar: (z: 3)). EnvirGui just displays the sub-environments as text fields, i.e. the above just gives a 2-text-field gui instead of 3 sliders.