Open the Error Check Window by clicking on the Error Count in the Debugging Toolbar:
The Error Check Window shows any setup errors that the Error Checker finds in your project:
The message includes the full path to the error:
Game Object Name : FSM Name : State Name : Action Name : Field Name
Click on the error message to jump directly to the error.
When the game is running the Error Check Window shows Runtime Errors in the same format, so you can quickly find errors in FSMs.
If the editor is slowing down in larger projects you can disable real-time error checking in Preferences:
Preferences > Debugging > Enable Real-Time Error Checker
NOTE: You can manually refresh the error list using the Refresh button.