Add an option to disable specific sequences

[aer0aa]

I think there should be an option to disable specific sequences. This would be useful if you wanted to add a sequence that starts with the other sequence e.g. Normally, if you wanted to make one that starts with l and t, you wouldn't be able to because of the shortcut for "<" unless you disable every sequence in the Xorg project, which also disables a lot of useful ones. If you could just disable that one, it'd be much more convenient

[JamesFrankel]

This would be really useful!

[psymar]

This has been listed as an issue before but was marked "fixed" by the option to disable entire classes of default sequences, which doesn't help. I think there's a rule that custom sequences override default sequences, but I shouldn't have to make a custom sequence to make a default sequence (compose o -) work, which as it is it gives the wrong symbol unless I disable the xcompose sequences (this is one where the xorg and xcompose sets clash -- I wanted ō not "masculine ordinal indicator" whatever that is.)