Copy and paste (Ctrl + C / Ctrl + V) is by default shared between all/certain Qubes.
Perhaps have settings where you can choose which Qubes can/cannot access the clipboard by default, and only for those certain Qubes you must use
“Ctrl + Shift + (C / V)”.
In my personal opinion, this makes working (especially for new users) much easier. I also think that this level of security is an option that you can choose opt in to.
My other suggestion is to have a “similar” thing for folders, where we have one folder for certain Qubes to share?
Just thinking out load
Thank you for reading.