How can I manually split sharedassets0?

I’m developing a PC game like Flight Simulator.
Recently I add some big terrains to my scene. After that, it runs well in editor but not in builds.
All I can see is black background with UI. FPS is also bad.

I think too big file is the problem. sharedassets0.aseets is over 7GB.
In other project, it has more than 2 files but just one in here.

So, I wanna split it manually but I cannot find setting about it.

Is there any way to control it?

I don’t think that splitting shared assets will make any difference. It’s basically all the assets from your scene. Even if you split them up, all of them would be loaded because of it.
What you probably need is dynamic loading content. Only load what you see, or need. Unity’s Resources class is your friend here and while we’re talking about splitting, everything you dynamically load has to be placed into a Resources folder in the folder structure, which which put more assets into the resources.assets file.