Currently MarkerBox.do_button_press_event takes care of the interactions with markers. The logic which creates/removes/edits a marker should be refactored into actions which can be assigned keyboard shortcuts. https://gitlab.gnome.org/GNOME/pitivi/-/blob/master/pitivi/timeline/markers.py#L166

See here for an example of how to add an action: 8d1f7644 The Gio.SimpleAction objects should be created in the MarkerBox class and added to a group = Gio.SimpleActionGroup() which can then be added to a widget or container to make the keyboard shortcuts available while the widget is focused. For example in the TimelineContainer class we could have:

self.timeline.insert_action_group("marker", self.markers.action_group)`