While there is quite obviously an option to specify how frequently the trees spawn, there isn't one for volcanoes. While I am quite fond of them myself, one of the biomes I passed over while exploring had a row of 6-7 volcanoes all glued together.

This screenshot is a very minor example of the volcanoes being glued together: https://i.imgur.com/Emm1xfq.jpg

The volcanoes at least feel as though they would be better if they were more infrequent, while having a lot of trees gives a really interesting feel to the tree biome.

your suggestion is added in my fork(indev) : https://github.com/quentin452/enderoni-continuation

(I haven't actually looked at any of the source code to see if this is possible, just doing a bunch of things while on lunch break. If it is simple to implement (I'll try to look later), I might just do it myself and issue a pull request. Thanks again for a visually amazing mod!)

I doubt this mod will ever be active. Unless you're willing to continue this mod, then its dead.