In 6.x-2.x any group you wanted to use in the UI had to be declared in the .info file. The syntax was as follows:

; Groups
skinr[options][groups][links][title] = Links
skinr[options][groups][links][collapsed] = 1

Skinr 7.x-2.x implements four default groups: default, box, typography, layout. Any skin that doesn't declare a group will be added to 'general' and you may add any skin to the other groups without the need to create them. If you want to use a group not supplied you will need to create it. The way to do that is to use hook_skinr_group_info(). The syntax for creating a group just like the links group above is:

 * Implements hook_skinr_group_info().
function MYTHEME_skinr_group_info() {
$groups['MYTHEME_links'] = array(
'title' => t('Links'),
'description' => t('Description for administrators.'),
'weight' => 0

As you can see you do not have the option to set the group as collapsed or not, this is because skins are displayed in vertical tabs and not fieldsets. For more detailed information about working with groups click here.