I hadn't, I read the OP and it stated SVDT already decompresses it.
However, I did try to decompress it myself and I got a error.
Oh, sorry. I think I wrote it wrong in the OP. I'll fix it.
Save Data Magener and svdt give you the file already
decrypted. That's different to
decompressed. SaveDataFiler (an older tool) gave you the file encrypted, so you needed to
decrypt it first. And after being decrypted (which SDM and svdt already do), we need to
decompress them.
I'm working on implementing the
decompressing into the editor, so you can load a file taken directly out from SDM or svdt, but right now
you need this tool for decompressing:
https://github.com/SciresM/FEAST/releases (Fire Emblem Awakening Save Tool 1.1). And you'll need to
compress again after you edited using the FireEditor.
Be sure to download the 1.1 version, since 1.0 had problems when decompressing some times. Sorry for the inconvenience. My update with included decompression will be out in the following weeks.