Prediction: you will want to write your own terrain paging before too much longer.
I don’t think JME’s terrain is designed to do what you want… so you will be fighting it a lot. It also does some things that I personally find kind of dumb (the edge stitching is totally unnecessary for example).
For alternative approaches, you could look at this paging library:
It just manages the grid, the background threads, and scene interaction (kind of) for you. The specific mesh generation, etc. is up to you but it would let you use more classic approaches.
The downside is that it’s not well documented. It’s reasonably straight forward, I guess… and you can see how it is used ‘in action’ here:
It manages the terrain and trees/grass in that demo but should just as easily help manage LOD “pyramids” which I think is what you are describing.
Here’s a video of the demo:
It’s not a cookie cutter solution for sure… but maybe it helps when you’ve hit bottom on JME’s terrain.