Problem: Suppose you are browsing a certain category on Wikimedia Commons. Using Cat-a-lot, you decide to pick a couple of files and add another category to them. The new category will be automatically added next to the category you are browsing. But you might wish that the new category will be inserted before the category you are currently browsing, instead of after it, if you think the order of categories of files important. Currently, Cat-a-lot doesn't allow you to do this.
Proposed solution: Make it possible for a user to choose that a new category be inserted either before or after the current category.