After opening, one has to exit by clicking outside the button drop-down.
A second click on the button should suffice but it just closes and opens.
Extra clicks are required to perform an action within the drop-down e.g. to switch off View > Multi-book view.
The View > Locator_bar button acts as a switch in the way the first three buttons should act.
There should be consistency and economy of operation as with the non-subscriber toolbar.