If you've gotten bored of your current world or you just want to start over, you can easily reset it. This tutorial does not cover custom generators.
Select the server you want to reset the world for from the panel.
Ensure the server is stopped to prevent problems.
Open the file manager, then compress and download a backup of the server with the `...` button along the right, as the following is irreversible.
Select `...` for the world after downloading a backup of it then click delete.
Start the server and a new world will be generated.
NOTE: Generating a new world may cause the server to take a few more seconds to load for the first time.