After trying to create a theme that fails even as a simple "person" fork with custom css I decided to create a repository with additional css to modify this theme from the custom css box.

I would like more information to create themes but I see it difficult for now. However, I leave my edition for those who want to try it and surely extend it a little more.

GitHub - Vasak-Group/nodebb-theme-vsk-community: Community Theme para NodeBB

Community Theme para NodeBB. Contribute to Vasak-Group/nodebb-theme-vsk-community development by creating an account on GitHub.

GitHub (github.com)