Can't get toolbar buttons onto the main ("unified") toolbar

[eyalroz]

With TB 115, the proper toolbar of the 3-pane window has been nixed, in favor of a weird sort-of-a-toolbar above the menu bar. Unfortunately, it is quite challenging to overload that bar with buttons, as it has the customization mechanism like the old toolbar, but - not quite like it, and seems to be deleting potential buttons it doesn't like.

We need to figure out how to get the buttons up there.