Adding Tabs/Toolbars to the Admin Toolbar
Only one toolbar is visible at a time on the Admin Toolbar. Links to each toolbar on the Admin Toolbar appear as tabs at the top.
Clicking on a tab allows the administrator to switch to that toolbar.
Which toolbar is currently active affects which slots are visible on the page, the options that an administrator sees when interacting with each slot, and which sections/buttons appear on the Admin Toolbar.
