99% of the time I use Built-in RP, and unfortunately I don't know what can replace RTP for URP.

I'm mostly an application programmer and have very little experience with shaders, so I definitely can't make such a tool, and unfortunately I can't even give you a direction to start digging.

At the moment (in 2018) I am using your RWT asset and an asset that works well with yours called RTP (Relief Terrain).

It's a tool that allows me to switch, when I get close to the terrain with the camera, from the real google/bing texture to a 4/8 layer shader and transform the terrain into sand, grass, rock etc.
Unfortunately this RTP doesn't work in URP and I need to use this render pipeline.

I was wondering if you knew any system to achieve a similar result?

RTP works by saving the Steepness and Height maps of the terrain tiles generated with RWT and, through a Combined Heightmaps texture, allows you to automatic paint the various layers (sand, grass,..) on the terrain in a perfectly correct way, by modifying other parameters too.
(You can see RTP interface attached)

I was wondering, could this result also be achieved using terrain tile splatmaps?
And could you create a tool that extrapolates these splatmaps from the generated RWT terrain?

Thanks a lot for your time