There’s currently not a way to do this. We often get this request, but it would be much less useful than people think. The reason is twofold.
First, it wouldn’t reduce bandwidth and load times as much as you might expect. Because of 3D Tiles’ hierarchical LOD structure, tiles in the distance are bigger and lower resolution, and there are far fewer of them. So skipping them entirely would only reduce the total number of tiles a little bit. It wouldn’t make a big difference.
Second, setting a distance in M/KM wouldn’t actually work that well. The view distance you need is highly dependent on the camera height. For applications with a fixed camera height you might get away with it, but most applications have a mix of near and far views, so a single view distance wouldn’t work.
Internally, cesium-native has a thing called a fogDensityTable:
It’s a bit inscrutable, which is why we haven’t exposed it up through Cesium for Unreal, but the basic idea is that objects that are really far away don’t need to be rendered, and the meaning of “really far away” is a function of camera height. So potentially tweaking that could help achieve your goal. But again, the gains to be had here are quite modest. I’d roughly estimate you could achieve maybe a 10-20% reduction in tile loads by bringing in the view distances, not more than that. And at the cost of having mountains vanish in the distance.