Spent half a day trying to upload a world via file manager, thinking that uploading a zip file was enough. Not at all. The uploaded zip file appears in the uploads subfolder in the file manager. It needs to be unzipped there (once the file is selected, the menu at the bottom of the screen will offer to unzip), and then moved to the Home folder. Once this was done, I chose the level name as the name of my world folder, saved and restarted the folder. It is possible to switch between the worlds via Multiverse, but before that the world needs to be unzipped as above, otherwise, Multiverse just creates a new world under the chosen name.
