Running Blueprints in the Editor
Any time you use a Custom Event node in the Event Graph of a Blueprint class, you can set the Graph > Call in Editor option in the Details panel:
Similarly, when you create a new function on a Blueprint class, you can set the same option in the Details panel:
If you place an Actor that has a Custom Event or Function like this into a Level, and you select it in the Viewport or in the World Outliner, the Details panel will show a button for each of these Call in Editor events and functions you set up. You'll typically find them in the Default section, where Blueprint classes also expose variables.
Click this button to trigger execution of the Event Graph from your Custom Event node or to trigger your custom function.
This works for any Blueprint class that you can place into a Level. You can use it to test your runtime gameplay, as well as to build Editor-only content management tools.
If your Custom Event or function has any inputs, it will not be shown in the Details panel.