It is not like a global back command would suddenly solve this problem; every app would need to implement what 'back' means to it. The inconsistent nature of what back means on an Android system is always a frustration to me, and I think it solves fewer problems than it causes.

Sure in Morph it would be very obvious what back does, but I'd argue that an option to move the navigation bar to the bottom edge would be more useful. Half of the apps I regularly use don't have an obvious 'back' action; what should 'back' do when I'm viewing maps in Pure Maps, or when typing into the calculator? I agree with others that each app should consider this as oppsed to forcing a global option.

Back and Home are UI hangovers that have been improved away by the Lomiri UI. ☺