UE4 v4.9.1 - blank bp project, optimise for mobile, scaled graphics, no default content

create MyGameMode (gamemode)
create MyPlayerController (player controller)
create UI_level1 (user widget)
create UI_level2 (user widget)
create UI_level3a (user widget)
create UI_level3b (user widget)
create UI_level3c (user widget)
create UI_level3a_sub (user widget)
create UI_level3b_sub (user widget)
create UI_level3c_sub (user widget)

edit UI_level1, drag in UI_level2
edit UI_level2, add a widget switcher, drag UI_level3a UI_level3b UI_level3c into the widget switcher
edit UI_level3a, drag in UI_level3a_sub [also do this for 3b and 3c]
add a text box to the 'sub' widgets so you can see which one is visible

edit MyPlayerController, create UI_level1 and add it to viewport, add input to 1,2 and 3 to set the widget switcher index to 0,1 and 2
set world properties to use MyGameMode and MyPlayerController

compile and save everything

PIE

At this point it should run and let you switch between the three widget pages and correctly show each one on screen as you switch with the keys assigned in MyPlayerController

Close the editor, reopen the project.

PIE

This test project works, my main project will result in the RPG tab not showing anything and the [REINST] note showing up on hover.