The spawn chance is configurable in the MelonPreferences.cfg (i.e. C:\Program Files (x86)\Steam\steamapps\common\Slime Rancher 2\Mods) Copy MoreYolkySlimes.dll to the Mods folder in your Slime Rancher 2 install folder (i.e.Install Melon Loader for Slime Rancher 2.It only adjusts the spawn chance on existing spawn points.

This mod does not add additional spawn points for Yolky Slimes. Slime Rancher 2 mod that increases (or decreases) the spawn chance of Yolky Slimes.