It seem like a very basic question but I failed to find something...

I want to create "categories" for all my project. Something like "game made in 2018" and "game made in 2017" for example, to sort them. 

You can show the game you have in your library alongside your projects, with their own categories and even rename them but I didn't find something like that for your projects.

Thanks !

To the best of my knowledge, the only way to do that now is to hide your games on the creator profile and only show them in collections below. (You can put your own games in collections just fine,) Reordering them may also help with grouping.