It would be really useful to have soft shadows from stationary lights like you can by using the source radius parameter for static lights ?
Are there any plans for this ?
If both types of lights are simply baking shadow maps using lightmass I can’t really understand why one supports the function and the other one doesn’t.
You might have to increase the resolution for the meshes that aren’t casting shadows, the setting is in the Static Mesh editor
Make sure to go over the documentation: Distance Field Soft Shadows | Unreal Engine Documentation
I think you can still use it with lightmass.