In Patrols I want the groups.MyGroups table to be in display mode LIST in the dashboard of a mobile device. But the client doesn't report the available width when asking for a dashboard widget.

I can set default_display_modes to {None: "list"}. The 'grid' display mode is always available ven when there is plenty of room, but when user opens it in its own window, there should be a way to manually switch to GRID mode.

Just

you can't disable it (except by setting hide_navigator to True).