The Bookmarks tab shows the active PDF's current bookmarks.
Go to View > Tabs > Bookmarks or press ALT+B to open the Bookmarks tab.
Bookmarks are arranged in a Bookmarks list. Click the name of any bookmark to initiate the bookmark's action.
Bookmarks can be arranged in a typical parent-child structure, shown by the presence of a toggle arrow to the left of a bookmark's name. Click any toggle arrow to hide/reveal that bookmark's child bookmarks.
Bookmarks that are located on the page currently being viewed in the main workspace will have a triangular icon to their right.