Something I happened upon by sheer accident

Don't know if this will work in other browsers...I use Firefox...

After you've got your drop-down menu there...highlight the top one...hold the Shift key down...and press and hold Delete...

It should automatically scroll deleting almost everything in it's path.

Or...to delete individually...just press delete as you require.

Eg

EDIT: I know there are easier ways in IE to do this...but...all the same...

Just tried it in IE...you can do it there too...but you have to repeatedly hit the delete button...you can't hold it down too...so...you can do IE this way but you have to do it one at a time...fast-fire

Apparently it works in all drop-down search boxes...I just cleared my PM menu the same way.