In Orion, extensions take up a significant portion of the toolbar.
They can be moved into the overflow menu, but that's a generic menu for any toolbar item.
A better implementation of the extensions in the toolbar would be:
The toolbar has an extensions button which is a popover that displays all your extensions as icons.
When the icon for an extension is pressed, it shows its settings.
From that popover, you can drag the extension into the toolbar if you wish to have it 'pinned'.
This feature will provide the user with better UX, and save on limited toolbar space.