Operating system or device, Godot version, GPU Model and driver (if graphics related): Windows 10, Godot Git 409e58e, NVIDIA
SpotLights with shadows enabled cause shading artifacts to appear in the editor, see the screenshots below. Tweaking the shadow bias doesn't seem to have any effect on the artifacts.
Narrow spotlight with shadows (broken):

Wide spotlight with shadows (broken):

SpotLights with an angle above 90° look broken with shadows enabled, but they work with shadows disabled.
Ultrawide spotlight with shadows (broken):

Ultrawide spotlight without shadows (working):

This bug doesn't seem to affect running projects.
SpotLight in running project (working):
