How do you use this program to extract and insert save files? I opened it up and it all looks really confusing.
Basically, you've 2 file explorer : the left column contains your CIA or cart's savefiles, while the right one is a SD card file explorer.
You can move your cursor between those two using the stick & arrows, then if you press Y it'll transfer the thing you're on to the other column, in the folder it's currently opened (if you press Y on a file/folder it'll transfer it, and if you press Y on the "..." symbol at the top of either column it'll transfer all content from active directory). You may need to press select to confirm if pressing Y leads to overwriting something.
You can see all those instructions on the bottom screen (press select to make them reappear).
Now to export a save you have 2 options :
One, when you launch svdt it'll automatically export the savefiles in SD:/svdt/<game>/<date>/. You can then press start to quit svdt right on the first screen.
Two, you can navigate through folders and use Y on the leftcolumn to transfer the savefiles to the location of your choice on the right one. This is not very useful unless you want to put the save somewhere precisely on your SD card.
Then, to import back a save :
Open svdt, if you selected a game installed on your SD card (not a cart), the game will ask if you want to overwrite secure value. Press A or your imported save may be detected as corrupted (it has no effect on exporting the save so press either A or B if you don't wish to import).
Then, navigate to the folder containing your savefiles, in the svdt folder or wherever you put it, and press Y to transfer the savefiles on the right column to the left one (remember, press Y on "..." to transfer all files at once). It'll likely overwrite something, so you'll need to press select to confirm.
You can then quit svdt and launch your game.
PS: when you launch svdt, everything on the left column is your save, it may be a single file or multiple folders but you need to transfer them all. If that's the case, remember pressing Y on the "..." line.