Trigger to close an object when tab focus moves from it?

Hi Tom. Thank you so much for your reply. Although I can't share my course, because it has proprietary information, I put together a simplified example in the attached file.

I managed to discover that you can program anything to hide upon a key press. The Enter key works now for closing the popups, but the Tab key does not work in the same way. (The file contains a detailed description of what's wrong, and why I think I have discovered a bug.) 

Although the Enter key works pretty well, I would prefer the Tab key for a couple of reasons. (1) It would require only one keystroke to simultaneously close the popup and move tab focus to the next button, and (2) it would not lose the yellow tab focus box. By comparison, the Enter key requires two keystrokes: Enter to close the popup (which makes the yellow box disappear--potentially disorienting), and then Tab to move the tab focus to the next button.

Thank you so much for your help!