Joined: 1 Apr 2013
Post Likes: 0
Some abilities are "passive," meaning that they're always on and won't have an icon.
If you're referring to the skill tree, you'll only get to use the skills you have equipped to your buster.
If you're trying to find the skill tree to select your skills, go to the main base and click on any buster. From there you can see their stats like attack and defense, change their equipment, select skills, and yes choose another buster in the same menu box (that way you don't have to hunt throughout the building to edit each buster one by one).