In Settings - Keyboard I have added custom shortcut by press on +.
When I try to set shortcut I can't enter nothing. Why so?
Ask Ubuntu is a question and answer site for Ubuntu users and developers. It only takes a minute to sign up.Sign up to join this community
I found solution. Firstly, I should delete desirable combination if it uses as shortcut in another command.
I found desirable combination on the list on Keyboard settings, then selected this field and pressed Backspace to reset combination from this command.
Now I can set desirable combination to my custom shortcut.
The procedure is indeed not very obvious on first time use. You observed that when you clicked +, the Add Custom Shortcut dialog appears. It contains the fields "Name", "Command" and "Shortcut".
To change the shortcut, click the little left-arrow with a cross in it on the right of the current shortcut combination. Now you can set a different combination the same way as above.