[MlMt] Quick refresh of smart mailbox?

[Quentin Stafford-Fraser]

Is there a quick way to refresh the view of a smart mailbox?

I use a combined 'Unread or flagged' box as a kind of to-do list, as per
http://www.statusq.org/archives/2014/08/27/6007/

It would be very satisfying, once I've dealt with an issue and unflagged 
it, to hit a keystroke and see things vanish from the list.  At present, 
I switch to another mailbox and switch back...

Quentin