Smooth fog transitions (World Renderer plugin 2024.2)

I really can't seem to figure out how to make fog transition smoothly from the default start/end point to the new one. This is for a biome. I want the fog to get closer as you enter the biome and further as you exit. I tried a bunch of things, but none of it worked. I'm open to editing the code directly.
Feel free to ask for more details.

Thanks.