PKHeX VS NieR.Automata.Editor

I'd eat my shoe if the dude wasn't just using exactly that https://github.com/kwsch/PKHeX

.state files are not supported, according to the readme here. (disclaimer: I never used PKHex myself though)

https://github.com/kwsch/PKHeX/tree/master/PKHeX.Core/PKM has lists of specifications for all the data structure formats that have been used over the years.

There is also a save game editor for Windows implemented in C#, which can be used to move/trade Pokemon: GitHub - kwsch/PKHeX: Pokémon Save File Editor

It's called PKHex. Here is a link to the file

Maybe possible with pk3DS or you can try editing your save file with PKHeX.

According to PkHeX data it is shiny locked... Source

If you'd prefer to save edit one in you can use PKHeX.

What you can try is: start new game on the new crack and play until you can save, and save. Then use this save editor to take note of the steamid64 embed in the new save. Then copy your old saves in the new save folder, and use the save editor again to modify the steamid64 of these old saves to match the one you took note of previously.

to add onto the replies you've got now: a quick search for a save editor gave me this tool to set your XP (and by extension, level) to whatever you want, in case you want to put yourself back at-level without grinding up to 99 and hoping you can get through that one hell-arena