@yukinoh1989 You can find the “preinstalled” ones where you have Blender 2.8 installed under the 2.80->Datafiles->StudioLights->World folder
I just tested it (using the 2.8 version from week before last) and it seems you CAN add AND delete images from this folder and have them available for the LookDev. Most of the ones in there by default are a lower quality HDRI that aren’t suitable for renders (Which is why the background was blurry in my day scene from last week). But if you do put higher quality one in there, it’s basically super blurred in the LookDev (unless you see it through any reflections or refractions).
