https://searchfox.org/mozilla-central/rev/1f4e023df8ff04b893ca792492f1e2e9629bfddb/toolkit/modules/ShortcutUtils.jsm#315 and https://searchfox.org/mozilla-central/rev/1f4e023df8ff04b893ca792492f1e2e9629bfddb/toolkit/modules/ShortcutUtils.jsm#287 The error "shortcuts-system" is the one thrown when you try to bind to one via the UI. OTOH no error is thrown if you bind using the API rather than the GUI, so maybe getting rid of these checks isn't good enough.
https://searchfox.org/mozilla-central/rev/1f4e023df8ff04b893ca792492f1e2e9629bfddb/toolkit/modules/ShortcutUtils.jsm#315
and
https://searchfox.org/mozilla-central/rev/1f4e023df8ff04b893ca792492f1e2e9629bfddb/toolkit/modules/ShortcutUtils.jsm#287
The error "shortcuts-system" is the one thrown when you try to bind to one via the UI.
OTOH no error is thrown if you bind using the API rather than the GUI, so maybe getting rid of these checks isn't good enough.