Can the site be configured so that you only get to see the posts in categories and with tags that you define in the User Preferences when you click on your icon or some other UI element, instead of having to select them manually at every visit?
If you mean those at /u/$USERNAME/preferences/categories and /u/$USERNAME/preferences/tags, they stick here and I certainly don’t need to redefine them at every visit.
You can mute tags and categories you don’t want to see. Unfortunately the other way around (selecting only the categories/tags you don’t want to see) is AFAIK not possible right now. See rdm#2952 notes #67 to #72.