How do you scroll down the collections bar?

When you see something to add to your collection and have more than 2 collections already, how do you scroll down? I press the down button but it doesn't do anything.

Not meet such problem yet, did you tried pressing the "End" Key?
I'm afraid I have not had this problem... I have 3 in my list, and yet the list expands for me. Perhaps the issue is related to the browser? I am currently using the newest version of Google Chrome, and it is working just fine for me.