Hi Matthias,
Actually this is already done, but you may need to turn on a Preferences setting to actually use that size when restoring sessions.

Open the Preferences and go to the Window section.  Make sure that "Resize graphics window on session restore" is checked on, then click Save so that it will apply to later uses of ChimeraX.

In agreement with you, I personally prefer this option to be turned on, even though the initial default is off.

Preferences (Settings):
<https://rbvi.ucsf.edu/chimerax/docs/user/preferences.html>
... Window section:
<https://rbvi.ucsf.edu/chimerax/docs/user/preferences.html#window>

I hope this helps,
Elaine
-----
Elaine C. Meng, Ph.D.                      
UCSF Chimera(X) team
Department of Pharmaceutical Chemistry
University of California, San Francisco


> On Nov 18, 2021, at 9:03 AM, mailman-bounces--- via ChimeraX-users <chimerax-users@cgl.ucsf.edu> wrote:
>
> From: Vorländer,Matthias Kopano <matthias.vorlaender@imp.ac.at>
> Date: November 18, 2021 at 8:47:33 AM PST
>
> Dear all, 
> I would like to suggest that the current windowsize is associated with a ChimeraX session. This is particularly useful when making figures in a reproducible manner (if I am not mistaken, when opening a .cxs file it will open it with the same windowsize that has been used for the last chimera session, rather than the one that was used when the session was created). I am aware that the windowsize can be specified in a script file.
> 
> Thanks a lot for your consideration : )
> Best,
> Matthias