See also the Compiling Blueprints section above.
While playing the game, you can press Shift + F1 to regain the mouse without having to exit the game. If you then switch to one of your Blueprints, you can see when events are triggered.
You can also right-click on variables, inputs, and outputs and watch variables while the game is running.
The <Print String> is a very useful node for debugging your Blueprint systems. You can use it to print text or ...