Non-Whonix specific question.
As per Free Support for Whonix ™ and
https://forums.whonix.org/t/what-to-post-in-this-qubes-whonix-forum-and-what-not
I suggest to rephrase this question:
“Is it possible to install a Qubes Template and/or Qubes VM on a
different partition?” or something like and I suggest to ask the Qubes
support since they are more qualified to answer this Qubes specific
question.
(I don’t know. Quite possibly it can be done. No idea.)