@deshmukh
In Appearance > Menus make sure Buddypress is ticked in screen options. That takes care of user links.
To link to a specific group, I would just create a custom link as you would do for any other link type.
@style960 thanks for suggesting selecting ‘Buddypress’ in screen options.
But that does not solve my problem. How does one provide a link to /groups/groupname/admin, for instance?
@deshmukh You could use the ‘Links’ menu type and create custom links where you enter the title and URL manually.