In this tutorial, we take a look at how a combo box in the widget blueprint can be populated or created with an outside array and used to triggered program or other logic in your project or game. Since we couldn’t find many tutorials on the combo box, we thought we would make one to help keep things current. The combo box is a surprisingly complex and powerful widget in the blueprint.
https://dev.epicgames.com/community/learning/tutorials/BJ17/unreal-engine-using-an-array-to-make-a-combo-box-and-what-to-do-next