What problem does this address?

While working on adding right click support to the list view over in #50273 I've run into an issue with the block settings menu (or dropdowns in general) when right clicking into the browser window while another browser window is active. When doing so (on a Mac at least), right clicking doesn't shift focus to the browser window, so a click event will happen, but focusing inside a dropdown does not. This means that the focus outside behaviour of dropdown menus doesn't work, so it's possible to open multiple block settings menu within the list view.

To replicate without that PR, you can CMD+click from another browser window into an inactive post editor browser window, and click in the general area of the block settings menu buttons. This will open up multiple block settings menus without the already open ones closing.

Screenshot of the issue

It's a little hard to see in this screenshot, but there are multiple block settings menus open:

Screengrab of the issue

This should hopefully be a little clearer. In this screengrab, I have another browser window active, and then I CMD+Click into the inactive window with the block editor open, and click on the list view block settings menu buttons to open multiple block settings menus. The issue feels pretty edge-casey in isolation, but with #50273 (introducing right-click behaviour) the issue will be more prominent, so I'm hoping we can look into a fix.

What is your proposed solution?

I think it'd be good if we can somehow ensure that only one block settings menu is open at a time, possibly by storing state somewhere of the instance of the latest opened block settings menu? Then we could have a useEffect or something of the like the block settings menu that checks if the currently opened block settings menu id matches the current id, and if not, it closes the menu.

I'm not sure how do-able that is, and I see that the v2 DropdownMenu introduced in #49473 allows for open as a controlled value, so perhaps that component might make it easier to achieve.

I was a little stumped attempting to fix this over in #50273, so thought I'd open up this issue in isolation in case folks have ideas on how to implement it. Would love to hear ideas!