Can I create VCA fader to a group of VCAs/Groups?

Cubase
2

Yes, VCAs can control VCAs

but

VCAs are pretty buggy, they have an unresolved flaw that has yet to be fixed. so I’d avoid them for now.

see:
is VCA safe to use now ? - Nuendo - Steinberg Forums

VCA BUG? - Nuendo - Steinberg Forums

VCA problem - Nuendo - Steinberg Forums

VCAs still broken - Nuendo - Steinberg Forums