Favorites
Contacts and Companies that are tagged as Favorites appear in the Favorites section accessible from the main screen on the mobile, or the Left pane menu from the web.
To place a Contact/Company in the Favorites list, edit the item, and add the group 'Favorites' in the Group field.
Group favorite (web only)
A group can also be set as a favorite. In the Edit Group screen, check 'Favorite': a shortcut to the Group appears in the Left pane menu on the web.