Downloading games from Wii U USB Helper is illegal, though everyone does it and nothing happens, so it's really a moral problem only.
As you have bought it from the eshop, I think you can download it without problem.
So I tried to copy and paste a level made in Miyamoto! level editor while the game was running in CEMU and it worked.
Just make sure you are on another level or the World Map.
This should make testing levels a lot easier.
Is anyone familiar with former forum opg.life ? I missed the transition to the new forum over the week end (was scuba diving in the sticks with no internet connection). If anyone in touch with any members please pm me.