Filamental's interface currently ships in 8 languages:
Open Settings (hamburger icon, top right) > General, and pick your language from the dropdown. It applies immediately, no restart needed.
Filamental will also try to detect your system language automatically on first launch. Whatever you pick is remembered on this machine and used every time you reopen the app.
This covers the app's interface: menus, buttons, tooltips, settings. It does not translate the content of your own worlds, your node titles and notes stay exactly as you wrote them.
Tell us.
See About & Welcome for how feedback works, translation fixes and new languages go through the same route as any other feature request.
Still stuck? Email [email protected].