I read through the answers and come up with my own solution / workaround to this problem.
It's something like this:
mklink /d "c:\data\network docs" "\\server\shareddata\"
originally asked here: How do I mount a network drive to a folder?
this does not create a new Z: drive but rather maps c:\data\network folder as a network share and then you can point your software just to this folder.
I was unable to fool CCleaner to scan for duplicate files on a Z: network drive but it worked on a mounted C:\share folder.
If you strictly need the share to represent a "drive" on your system - you can go 1 step further with: subst y: c:\share
sourced from: https://winaero.com/create-virtual-drive-from-a-folder-in-windows-10/