Thanks. And just for absolute clarification, can you confirm you're left clicking it please?

Try creating a new user for test purposes. Log in as that user, and advise if it behaves differently....

a. open multiiple windows of the same type.
Win key + e - repeat 3 times say.
Rt click on the f.explorer icon on the taskbar to display the jump list.
That's what I've shown.

See my post #3.
...

Well, the post says 'button':

332741

- just wondering- what were you expecting this to do?

I assume you're referring to the one below the jump list.