I have been trying to allow my worlds, containing hundreds of days of work, to be used in different devices. I've noticed a bug in this process which practically stops it from happening.

Minecraft appears to have its worlds to be able to be stored in two modes: "application" and "external." Application hides your worlds and makes them invisible to a file explorer, even with hidden files enabled. The worlds are stored in the app. External places them in the "worlds" folder of the game. 

However, after setting to external mode, my worlds don't show up in the files. They are still hidden. Creating a new world works perfectly fine, the world shows up in the "worlds" folder, but my old worlds, the ones I need to transfer, are still hidden.

Basically, setting to "external" mode doesn't do anything. Worlds are still within the application, when they should be exposed in the files. The worlds still disappear in-game when set to external mode, however.

For replication:

1. Create worlds. Make sure, that in the settings, worlds are stored in "application" mode. Notice the worlds are invisible when you check the files.
2. Change to "external" mode.
3. Create a world in external mode. Leave the game and check the files. Notice the world(s) you made while in application mode are still invisible, but there is the world you made in external mode.

What should have happened is that once the settings are set to "external" mode, the worlds you made while in "application" mode should be visible in the files. They aren't.

Thank you for reading this.