Unreal Engine 4
Saving your Game with Blueprints covers the basics, but it doesn't cover how to actually trigger the save (e.g. quick save or quickload).
The variables you need:
The full MySaveGame blueprint flow for saving and loading, by triggering events:
Triggering custom events within other blueprints from an existing blueprint - because you won't have access to the KeyInputs from the MySaveGame blueprint (they're only available for Actors, but the MySaveGame needs to extend from SaveGame):
If classes or events are not showing up, make sure that you hit "Compile" every now and again, so that these classes and events can be picked up.