Hi Vadym,
I've been following your work since 2013 and Terrasavr has been part of my Terraria routine for years, so first of all: thank you for keeping it alive this long.
When 1.4.5.7 came out the editor stopped saving correctly, and rather than just wait I decided to have a go at it myself. I've got a working build now that handles 1.4.5.7 properly, including the new items and prefixes. It's purely for my own use and I haven't shared it with anyone.
I'd like to send you the changes privately, in whatever form is most useful to you — a summary of what changed in the save format plus the updated ID tables, a diff, or the build itself. Whatever saves you the most time. If you think it's worth it, it's yours to use however you want; if not, no problem at all. Obviously I won't distribute anything without your say-so — it's your project.
I've also been working on a couple of additions that I think could be genuinely interesting, and I'd be happy to walk you through those too.
This is all non-commercial, just a fan who's admired your work for over a decade. I wasn't sure how to reach you directly — what's the best channel for you? Email, Discord, wherever suits.
Thanks for everything.