Tab cannot be used for keyboard shortcuts
Some software written for GTK lets users bind custom keyboard shortcuts, but Tab is reserved by GTK and cannot be used for keyboard shortcuts. This is problematic because ^Tab is somewhat of a convention for switching between tabs, supported by every major browser. GTK software (e.g. gnome-terminal) is forced to invent new bindings for this feature.
The gnome-terminal "bug" from users trying to set to ^Tab: https://bugzilla.gnome.org/show_bug.cgi?id=123994
Can GTK allow Tab to be used in keyboard bindings?