Hi,
Thanks for this nice program 
This is my first post.
I want to help to develope worldmachine.
I think Its a Bug:
At my first Monitor The Worldmachine shows all devices in tabs.
If I drag the Worldmachine-window to the second monitor I see it too.
But If I drag the size of the window bigger the tabs (and only the tabs) lost.
If I drag it then smaller and move back to the first window, the tabs missed continue.
After I click the button “maximize” in the right_top of the window at the first screen I get the tabs back.