@Thadeusz-Lay coz they may not want to use your theme. Making it a plugin will enable anyone to use it with any theme. If you want to keep things simple and don't want to publish your theme with custom fields, then you can add the fields in the theme.
I am planning to start a new forum but I don't like using its traditional layout that I want to use a layout like social networks out there (Facebook, Linkedin..) I found this forum https://smartphones.best/ matched my requirement to have a timeline on my forum homepage. I prefer its layout because comments can display below each topic.
The problem is my friend recommended me to use nodebb but I searched and not found any addons to do that. Does anyone knows how to create timeline for a forum? Please suggest me!
Thanks in advance.