Ive stumbled across this mod while searching for a way to keep my world clean and it appeared to me at first that the saplings wouldnt actually grow but now after 20h of simulated gametime the first growth has happened...
my question is now, if that is intended and then, if one could change something in the mod settings while setting up your world so trees grow faster ?

It is intended; tree growth speed is related to several factors, most significantly pollution and crowding of trees vs. their density at mapgen, and is soft-capped at a rate where max density (in a theoretical max density area from mapgen) forests generate fuel at the same rate as a max efficiency solar field.

It is my intention to add a setting to apply a multiplier to this in my next release/update, which I realize has been long in coming at this point.