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I've got net framework 4.7.2
No. Changing to a different key does not work. I tried two other keys with no effect.

Kappes Buur wrote: ↑Thu Dec 15, 2022 1:51 pm ....
2. in AppData/Local/Doom Builder find UDBuilder.cfg and UDBuilder.log
you can inspect them for clues, or you can delete them and let the editor generate new ones.
...

Could you upload the UDBuilder.log file?

UDBuilder.cfg would be more interesting.

Hurrah! Deleting UDBuilder.cfg helped!
It works!
Thank you!

Looks like Visual Mode is disabled for the "GZDoom: Doom (UDMF)" config. Go to Tools -> Game Configurations -> select GZDoom: Doom (UDMF) -> Modes tab -> check the checkbox next to Visual Mode at the bottom.

I've deleted the cfg. Now it works.
But anyway. Thank you very much for help.

Now. How to set that in the "Q" preview I would have full brightness?

Press B

Thanks!