How do i keep my levels from splitting up from my main level?

My asset levels after cooking my mod show up in the main Ark single player list. I have 4 asset Levels attached to my main level. But how do I combine all my Levels into my main Level with out over loading and lagging out my map. I know how to Level Stream my map But what do I need to do to keep all my Levels together and not have them save separate from each other? They show up in my main menu in single player as Main level: No Mans Land, NML_Foliage, NML_Rocks, NML_Landscape, When I go to play my map after cooking it instead of just my main level showing up in my single player mods list my asset list show up along side my main as if they where separate maps and I cant seem to combine them into my main. The map plays fine in the DevKit but as soon as I upload it to play on the main game it splits my levels up and forces me to play whatever level I click on. Is there some option I’m not selecting to combine them before I cook them? When I play my main my other levels aren’t attached to my main.