all you need to do is create a folder in the root of the sd card and name it IMEXPORT, copy the *.mid files there. Then go to the sd menu, sd tools, sd sound tools and use the sd sound import function to arrange the midis you select from the list into playlists which you can name and save. If you copy in bunches of eventual wanted playlists then just select all to save time. When done you can delete the original midis in the imexport folder to save space on the card.

The keysoft techmanager can load midis to sd on the pc as well as re-arrange end edit the midi playlists etc. Sd-explorer does not handle midis.