I searched around a little but couldn’t find a specific answer to my problem, apologies if this has been covered before.
What I want to do is: have a different workspace with its own resolution on each monitor.
Has anybody managed to config workspaces to a specific monitor while managing to keep them both independent resolution wise on XFCE?
I think it’s a question about XFCE, not specific to Qubes OS.
I assume that by “Workspace” you’re referring to some XFCE technology.
I can’t give you advice on XFCE-specific stuff, but I do a lot of multihead-stuff.
Also, I switched to i3 a long time ago.
XFCE should have on-board tools for letting you do display-related stuff.
From the Menu (assuming 4.2.1):
Click on “Q” → Gearwheel → System Settings → Settings Manager → Display
There is where you should configure everything to your liking.
If this does not help, run:
qubes-dom0-update arandr
inside dom0 of course
and type arandr in a terminal, oder select it from the menu.
It helps you composition your displays nicely.
It also offers you to export selected settings as an executable shell script that can be invoked either on start up or by just mving it to your desktop and double-clicking it for exeuction.
I think that QubesOS’ main DE is XFCE, and we should do our best to not let ppl hang in just because this is beyond qrexec.
XFCE itself doesn’t support this:
https://forum.xfce.org/viewtopic.php?id=15688
But there seems to be some workarounds that could achieve this on the level below XFCE.
Searching for the solution outside of Qubes OS forum would be much faster since the solution is not specific to Qubes OS.
I see. Thx for clarifying.
using Click on “Q” → Gearwheel → System Settings → Settings Manager → Display
qubes does not have any configuration available for different resolutions per workspace… 
thanks for your help anyway.