The last tab in the Custom usergroup section is Index.

This page is simply a list of all the custom and dynamic usergroups on your site, which you can search using the eye filter, for easier access.

From this page you can view, edit, Upload Members to and delete usergroups by clicking on the cog next to a usergroup record. You can additionally add completely new Custom and/or Dynamic usergroups from this section by clicking on the corresponding blue button at the top of the page.