Jesus Christ. I was reviewing the video, when it came into my attention the Action List has a cursor and help text. This means it must be made with the Window_Selectable class. :/
Now I basically have to start from scratch. To start with, I was working with a Sprite class, not a Window class.
EDIT: After finally analyzing the situation, I concluded the Final Fantasy XII Action List window has no specific format. Given the situation, I've decided to use the following format: each skill class will have its own page, each page will have three columns, at the top of the window there will be help text indicating a description of the skill, on top of the skills the skill class name will be shown, and at the left side of the skills, an icon of the skill class will be shown. If there are too many skills for a page, scrolling functions will ensue.
I should be able to finish tomorrow. Even though I was writing something completely different, I can recycle many of the methods I had previously worked on.