Blueprint communications between differente levels

My level is subdivided in 2 two sublevels: 1 for blueprints e 1 for lights
In my case I have a Switch blueprint that turn on/off a Light by reference (In my switch blueprint I have a public variable in which I put the light reference, existing in the scene, that I want to turns on/off).
The problem is that the light is in a different level and I cannot pick it up as a reference.
How can I make a communication between them even if they are in different levels?
Thank you in advance!

I tried to follow the istructions in the answer of Nachtmahr in the link you send me but I’m still don’t getting them. Could you help me?
What I’ve done works if all the blueprints are on the same level, but I need to separate levels and keep the stuff working.

Use A Blueprint Interface.

Are both levels loaded at run time or are you streaming it in or loading it later ?

If loading it later Have you considered setting an on/off Bool to the game instance and having the level set its lights based on the game instance Bool.

Edit: After rereading your question I am going to say you would need to use a game instance and set the variable in the game instance and then you should be able to call your game instance to read that variable. What I gathered from re reading is that you are trying to communicate between levels that don’t exists at the same time and the only way I know of is to set a public editable spawn exposed variable and pass the info when spawning or chuck my variables into my game instance and have my new map read those for settings.

1 level for blueprints, 1 level for lights. Both levels are loaded at run time.
The problem is that I have in the scene a Switch Object (to turning on/off light) where I must set, within the editor, the reference of a light situated in the scene (infact the public variable for the light is set in the construction script of the Switch Object).
In less words, I have a Switch Object connected to a specific light. When I aim the switch i’m able to turn on/off that specific light.

I don’t believe I understand. Could you post a picture of the blueprint in question ?

You want to flip the switch editor only and have it effect a light on another level ?

Sorry I am trying to help ya and need a greater understanding of what your trying to do.