There are differences with whonix 14 and whonix 15 intigration with Qubes helping tools like opening files in disposableVM , Transfer/Copy Files between VMs ... look at the images:
- Normal options for file.txt inside Qubes-Debian:
https://forums.whonix.org/uploads/default/original/2X/2/2390a319e48787095aa11a761b6d9d92e9285ada.png
- Options missed in Whonix 15:
https://forums.whonix.org/uploads/default/original/2X/c/cb479a69c8e651797ce4918b88617bf95292c31e.png