Idea for Rune/Mastery pages

Just a button that moves the page 1 slot to the left on the list of pages. I've suggested drag and drop before, but if the problem is the difficulty of implementation, this is easier to implement. If the page is the first on the list, the button is greyed out. For runes, bottom right, there's space for another button. For masteries, bottom left, there's a lot of space there.