I can help.
What you need:
1. Homebrew on switch OF COURSE
2. A micro SD card (32 gb is better)
3. Nut/checkpoint app for dumping and injecting save
4. HxD
5. Text editor
6. The 4th dimension (You must convert .bin file to .byml first before using it)
Have you watched Mizumi's tutorial?
Try this:
1. Go to USB loader GX and choose Hard Drive settings.
2. Choose Game/Install Paratition and change from FAT32 to NTFS
And there you have it!