Greetings @f.mazur,
Actually your overall idea of modifying the weston.ini file is correct, though there is a better way to do it then what you did.
For context when we build our containers we include a default weston.ini. This can be found here: debian-docker-images/weston at buster · toradex/debian-docker-images · GitHub
This gets copied to the usual spot in the container at /etc/xdg/weston/weston.ini.
So what you should do is overwrite this file when you start a weston-based container. You can do this simply via a bindmount. For example if you have your weston.ini in /home/torizon, then by adding the following to docker run: -v /home/torizon/weston.ini:/etc/xdg/weston/weston.ini
This option will take your weston.ini and overwrite the weston.ini that the container shipped with.
Alternatively you can also just rebuild the container with your weston.ini. That way you have your own variant on our weston container. Either of these options would be fine depending on your needs.
Best Regards,
Jeremias