One of the main apps you will need if your putting custom firmware on your 3DS/2DS:

GodMode9 Explorer by d0k3 is a full access file browser for the Nintendo 3DS console. It gives you access to your SD card, to the FAT partitions inside your SysNAND and EmuNAND and to basically anything else. Among other functionality you can copy, delete, rename files and create folders. You can find the source here.
Changes:
[new] Support for PNG (for splashes, script previews, screenshots) (thanks @Wolfvak)
[new] Display the SD FAT volume label in the drives listing
[fixed] Several smaller bugfixes and improvements
[deprecated] Deprecated PCX support in favor of PNG

via https://pdroms.de/nintendo-3ds/godmo...ds-application