https://mediafiles.urlaubsguru.de/wp-content/uploads/2019/07/Oberpfaelzer-Wald_Mystische-Waelder-am-Goldsteig-im-Naturpark-Steinwald.jpg
They are usually called "god rays" but the actual term is "crepuscular rays". If you search for a "god ray shader" you might find something you can port to Godot, I don't think it is included.
Godot 4 will also have volumetric fog, which can kinda get similar results. Here's a Reddit post when volumetric fog was just added (so it probably looks even better now), which kinda has the visual look.
