Assalam alaikum ..
There is an enhancement filed for populating users and adding them to buddly list targetted for 7.0. However I can see a hack at the end of the bug report, that populates buddy list from distribution lists.
24213
But till this comes out as a clean feature, I think you will have to manually add each user from 'create a buddy button', add a user, create a group name 'mygroup'. And everytime you add your preferred user, assign it to the group by filling up 'Friend Groups'. I hope this is what you are referring to.
Bugzilla
Wiki
Source
Buddy Group 
Linear Mode
