Found under: Settings > Set Actions > Delete
Whilst current sets are only available on the current device, these can be saved and then later loaded from set files.
All set files are stored in the /OpenSong/Sets/ folder. To better help organise your sets, OpenSongApp allows you to use categories. These are simply appended as text to the beginning of the set file name (compatible with the desktop version of OpenSong). Selecting a category will find all matching sets and display them on the screen. The MAIN category is for sets that haven't specified a category.
Select set file(s) to delete and then click on the Delete button. Please note that this action is permanent and you should make sure you have backed up your sets beforehand otherwise you won't be able to get them back!