See this thread from 2020. The temporary workround I found then no longer works, as Jim predicted would happen. Submenus can be attached to menu-bar menus and to popup menus in the data sheet, but not to popup menus in general.
See this thread from 2020. The temporary workround I found then no longer works, as Jim predicted would happen. Submenus can be attached to menu-bar menus and to popup menus in the data sheet, but not to popup menus in general.