You know, something silly happened – I wanted to give you a link, so I typed the subject into Google and clicked on a link at the end of the list without looking. And on that page, there was a modified version of this mod for ToE.
On one hand, I'm very happy right now, but on the other hand, I feel like a complete idiot, and I'm embarrassed. I can swear that for a week I couldn't find this mod for the right version. It's true that this mod is for 3.0, not 3.1, but I don't think there will be any problems.
Thank you for responding so quickly!
Sorry again!

P.S. – here's the link itself, maybe it will be useful to someone:
http://www.heroesofmightandmagic.com/heroes5/mods_and_fixes.shtml

Added 4 minutes later

And also, I didn't find a section specifically about mods on this site, so I created a topic here. Is there one, maybe I just didn't look carefully?