So instead I've modified my tool and here's texts.exe, which you copy in the same folder as the game (where player.exe is).
To extract texts, just run it, works with encrypted games too out-of-the-box. This will save "texts.csv", which you can open with Excel, LibreOffice, GoogleSheets, whatever and you can edit it as you please. Adding a new language is simple as adding a new column (you can copy'n'paste an entire column into a translator and then copy'n'paste the result back for example).
To update texts, run "texts.exe texts.csv". This will locate the "textList" array within the json, and it does not even parse what's before or after that (which is 99% of the file), just copies both verbatim, so it is blazing fast (less than a second on an over 50 Mb project.json). Even within the "textList" array, only "text" arrays are replaced, and only if there's a row in the csv with a matching id. Everything else, even the linebreaks are copied verbatim, so it is extremely safe to use, it won't mess up the json for sure (but it's always better to create a backup first).
