Mofi ...I will report IDM that assigning the ESC key is not possible anymore. I think the IDM developers can easily change it.
I've already had a couple of email exchanges with Troy at IDM, and he said the same thing.
If you still have the uedit32.kbd file or an UE prior v12.20, make the ESC assignment with the previous version. Than delete existing uedit32.uek, copy the uedit32.kbd to the INI directory and start UE v12.20. It will convert the .kbd file to .uek without any key assignment loss including the ESC key assignment.
FWIW, I erred when I said I've had the ESC key assigned to "FileClose" ... instead, it's always been assigned to "FileExit".
Over the past several hours I've tried your suggestion several times, with both upgrades and with clean installs of 12.20. Even though the ESC key assignment is always shown in 12.20's
Configuration > Keymapping, it doesn't always work (not
within an installation, but
from installation
to installation) ... sometimes it does, sometimes it doesn't. There's absolutely no consistency.
Press the button Show Key Mapping in Editor in the key mapping configuration dialog, close the dialog with Cancel and search for ESC in the file. Only the FileClose command should have ESC.
Even without hacking the file ESC is shown as assigned to "FileExit", even when it doesn't work.