Get items back on toolbar

Question

I have disabled an item in the Eclipse Luna (Service Release 1, 4.4.1) toolbar and now I can't get it back.

I have tried:

a) context menu / restore hidden toolbar entries

b) Window/Customize perspective.../Tool bar visibility

When I check the item in case b), it gives me the message

Make Item Visible

"New Wizards" cannot be made visible because it is in the unavailable "null" command group.

Would you like to switch to the Command Group Availability tab?

Yes No

However, it does neither switch to the "Command Groups Availability" tab, nor can I find it there when I navigate to that tab manually.

This also applies to other items in the toolbar, not only to "New Wizards".

c) Window/Reset perspective...

This works after restarting Eclipse.

Is there a way to get a toolbar item back without resetting the whole perspective?