I have checked past questions and this does not seem addressed. Blender 2.8.
How can I add additional transparency to a PNG imported as an Image Plane? E.g. make the entire picture half-transparent including it's normally non-transparent parts. For 2D images, I don't care about 3D at the moment.
Note I am not talking how to display existing alpha in a PNG, I know how that the Blend Mode needs to be set to Alpha for that for Eevee.
Also note that if it was a Reference Image, you can modify the alpha directly, but that does not show up in a render.
How to add additional transparency to a 2d Image Plane?