With the Profile Manager plugin you can customize the profile fields of both the users and the groups.
With this you could add a new custom field "My custom group id" and when you create/edit a group you can fill in this number. You can... view reply
Have a look at the plugin Translation Editor this plugin allows you to change all the translations on the site.
You can rename groups into 'communities' or whatever you want. It also has a search feature so you can easily find all the... view reply
i just tested the new version of this plugin on elgg 2.1 and i have found that when i view the list of friend requests to be approved for the recipient of the friend request, although 1 is shown in the topbar, i see no entries in the list...