Our keymap, when pressing Ctrl-Tab in Graph Editor, currently changes the space type to "Dope Sheet" with "wm.context_set_enum". But this method is not aware of subtypes. This PR instead changes the space type using "screen.space_type_set_or_cycle". While in Timeline it will go to Graph Editor, press again to go back to Timeline. While in Dope Sheet you go to Graph Editor, press again to go to Dope Sheet. Pull Request: https://projects.blender.org/blender/blender/pulls/141360