if #GtkShortcutsShortcut:shortcut-type is set to #GTK_SHORTCUT_ACCELERATOR.
The syntax of this property is (an extension of) the syntax understood by [gtk.global.acceleratorParse]. Multiple accelerators can be specified by separating them with a space, but keep in mind that the available width is limited. It is also possible to specify ranges of shortcuts, using `...` between the keys. Sequences of keys can be specified using a `+` or `&` between the keys.