How do I stream a sublevel using a especific key?

I’ll show you a pseudocode of what i want to do, I think it will be easier to understand.

I’ve been researching and I think the best way is to use sub-levels within the main level but I do not quite understand how to do that. Does someone know how should I do it?
Thanks!

I’m not sure if level streaming is really the way you want to go. If the user has the ability to spam the objects on and off quickly with a keystroke, level streaming may lag out or cause hitches. If it’s just a few objects, store them in an array and then cycle through them enabling/disabling as they press and release the key.

As far as assigning the functionality to a key goes, read this page about setting up and using inputs here: https://docs.unrealengine.com/en-US/Gameplay/Input