TOWUK_ru Flarum has support for a Display Name via third-party extensions. But no such extension exists at this point.
There are a few discussions about Display Names already, most notably this one https://discuss.flarum.org/d/408-display-name
If the feature you're describing is indeed the display name, please add your comments on the existing discussion above and I'll close this one as duplicate 😉 Otherwise, can you describe here in more details what you're trying to achieve ?
