This feature allows you to set up a bookmark list of other players. There are system categories, that have influence on starting games with other players or receiving messages and invitations from them. There are also user categories, that can be used to categorize the other players. And you are allowed to write down private notes on your contacts.
Go to the user-info of the player you want to add and follow the bottom-link "Add contact". If you already added the player, the link shows up as "Edit contact".
Activate system and user categories and enter an optional notes text for the user and then press the button "Save contact" to save it in your contact list.
System categories have influence on games and messages:
Hide waitingroom games: Hide game-offers in the waitingroom of certain user for the suitable-view. The game-offer is still shown for the all-games list.
Protect waitingroom games: Prevents user from joining your games in the waiting room
Reject messages: Reject messages sent to you by contact-user
Reject invitations: Reject game invitations sent to you by contact-user
User categories helps in categorizing contact-users:
Buddy: good friend
Student: student contact
Teacher: teacher contact
Fan: worshipped contact
Troll: mark contact-user as troll (for whatever reason)
DGS-Crew: contact supporting DGS in some way
Miscellaneous: as it has been decided not to provide customizable user categories, you can use this category to allow all kind of categorization by using keywords with a syntax you like in the Notes-field you can search for on the contact-list page.