How to 'observe this skill in action to learn it' in Crimson Desert

The whole idea that you can 'Observe this skill in action to learn it' in Crimson Desert is a lot of fun, since it's basically like unlocking an ability for free without having to use one of your precious Abyss Artifacts. All you need to do is observe the enemy, or boss in many cases, to learn their trick and turn it against them.

Skills that you can watch and learn are indicated in the skill tree, so maybe hold off purchasing these unless they feel vital to your playstyle. I guess if you found an enemy that performs the skill...