If the forum is too big for you and you're not interested in every single section, you can kind of blind out those parts.
First of all you have the possibility to fold away big sections of the forum:
But if you don't want to to fold away the whole section and want to keep some single subforums, then you can click on them and subscribe to them:
The result is, that you have all subforums you're interested in collected in your control panel:
And there's your custom and slim version of the forum.