There's not ab management for groups. So there isn't really a way to specifically change the order without just using pure CSS. Below is an example of how to do this with CSS.
Code:
.gjGroup .cbNavBarMenu > .cbNavBarItem {
order: 99;
}
.gjGroup .cbNavBarMenu > #cbtabnavgrouptabactivity {
order: 1;
}
.gjGroup .cbNavBarMenu > #cbtabnavgrouptabgallery {
order: 2;
}
This for example would order the Activity tab first, the Gallery tab second, and everything else as they already were ordered after it. Below is the #ID for each tab.
Activity = #cbtabnavgrouptabactivity
Gallery = #cbtabnavgrouptabgallery
Videos = #cbtabnavgrouptabvideo
Events = #cbtabnavgrouptabevents
Wall = #cbtabnavgrouptabwall
Photos = #cbtabnavgrouptabphoto
About = #cbtabnavgrouptababout
Forums = #cbtabnavgrouptabforums
Files = #cbtabnavgrouptabfile
Invites = #cbtabnavgrouptabinvites
With this you can order them however you like using purely CSS. Use CBs built in CSS overrides to save and apply your custom CSS as shown below.
www.joomlapolis.com/blog/kyle/18711-template-css-overrides-made-easy
In a future release GJ will have tab and field management once we've generalized that API in CB 3.x, but currently all that API is strictly tied to profiles.