If I got mc(1) right this should work, but it doesn't:
Escape sequences may be defined in
~/.config/mc/ini under the [terminal:foo-term] section.
F9 > Options > Learn keys provides a limited interface to these settings.
To change the completion key (
Alt+Tab by default), find the desired escape sequence through cat or other means, and add it to the complete key. For example:
Mouse support with unusual TERM
For some terminal definitions like
tmux-256color, mouse support doesn't work and has to be forced with
 seems to suggest it checks for kmous/smcup/rmcup, but these are present in all the above.