Thanks for your attention.I figured it out - it's so called "3rd level chooser key", and it's available as you said - under Keyboard-> Layouts -> Options... -> Key to choose 3rd level
and set it to left ALT
Solved.
Thanks for your attention.I figured it out - it's so called "3rd level chooser key", and it's available as you said - under Keyboard-> Layouts -> Options... -> Key to choose 3rd level
and set it to left ALT
Solved.