Hello! Sorry for the wait, didn't see your message last night and I woke up pretty recently.
Firstly, thank you for the kind words! As for a tutorial, I'm not sure if one exactly exists, but the best way I could redirect you to are (hopefully) existing tutorials for UndertaleModTool (the program used to translate the game.)
Despite its name, it allows users to decompile & mod the majority of GameMaker games, editing textures, code, etc. Problem is, it hasn't caught up with GMS2 yet so it can break pretty easily with those games - and wouldn't you know it, NO-SKIN is now on GMS2.
You might need to learn how to edit textures & fonts for some special characters and especially how to edit the game's code without fully destroying it which can be a tedious process but is a required one as that is where all of the game's text is located. Thankfully the majority of what needs to be translated doesn't cause issues, but some do require you to move around some variables and stuff - it sounds like a bit of a mess, but once you get the hang of it and learn what errors mean when playtesting, it gets pretty easy to identify glitches.
As for your question, for now you do need to start "from scratch" everytime a new update drops... but thankfully since the majority of the code stays intact (and the translation shouldn't really change much) it becomes more of a long process rather than a complicated one, just a bunch of copy-pasting already translated lines. Textures & fonts needed to be edited also need to be re-edited, and the latter can take a little while if many characters are added. I recommend keeping the old data.win file with you to be able to make things easier!
Sorry for the confusing mess this might be... I do also wish there was an easier way to do all this, but hey, I'd be lying if I said i wasn't expecting this to be complex lol. That's how it is trying to translate GameMaker games that aren't asking to be translated yet...!
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Hey! Thanks for answering!
I was taking a look at UndertaleModTool and It's not bad at all.
Adapting textures might be a challenge but I'll manage, pixelated fonts are way easier to edit than regular ones.
But I think I'll have to wait a bit longer since UMT can't edit these new files so yeah...
Here's hoping they update the tool!
Again, thanks for clarifying and have a good day!
EDIT: Nevermind, got it working! Time to test a few things lol