What does it try to solve?
Where did I trigger the animation? Where do I wait for input? Where did I use this variable again? Where was the FSM state that I wanted to improve? You know these problems. You have to click through FSMs which can be quite laborious, and you cannot see at a glance what's relevant for you.
Solution!
The solution comes in several stages. The basic one is a solution, the others make the feature even better.
Basic: Introducing State/Action Tags. The user can #hashtag words in the State Comment, which are then searchable. That way you can instantly see, and find, whatever is relevant for you.
Improved: In the improved version, the hashtags on a state are added automatically, when certain actions are added to a state (and removed accordingly). The user has to switch on an option, and then determine somewhere which actions should automatically add the hashtag to the state they're in. It's probably unwieldy to maintain a huge list, so how about an input field that is directly next to the manual and options button at the actions (but once set on an action, it obviously counts for all identical actions anywhere). It's first blank, but there you can set the tag's name and a label colour. See my quick mockups how it could function.
Use Case 1: You have a few places you aren't quite happy with. You simply add #WIP to the state's comment field. Weeks later, you have no idea where you wanted to make improvements. Luckily, you can use the tiny search bar, type in # and it shows you the hashtags you have used, or you when you remember that it was #WIP, you can type that in straight away. Click through the list in the hamburger menu next to it, and quickly go to the correct state.
Use Case 2: Suppose, you have some FSM and you are interested to know precisely where stuff is sent off to the animator. This can be quite hard to see, especially not at a glance, unless you use colour-coding which can be quite cryptic. Luckily, Playmaker now offers automatic hashtags! You go to the options and switch them on. Now a tiny label icon appears right next to the manual and options icon on the actions. You go find just one instance, say "Set Animator Bool", hit the label button, where you define the tag and a label colour. Et voila! Now everywhere where "Set Animator Bool" is used, you see the labels appended after the comment (if no comment, at the same place).
Use Case 3: Oh noes! You just cannot find any instance where you used "Set Animator Bool". No problem, just make a state anywhere, add the action, and then set the label. If you used the action already, they're now all visible. If not, fine, all future instances will be automatically labelled.