Merge Into Scene With Filter? Why doesn't it exist?
I just bought an asset that creates a set piece. The annoying thing about it is there's Cameras, Render Settings, individual elements, and a Scene file in the folder. Why isn't there a SET element? I don't want a Scene and i don't want to build it from scratch. But there's no way to load the scene without destroying my tone/env/render/sim settings. Sure, I could reload them. That's an extra step.
Actually, my real disappointment is that Daz doesn't have a filtered LOAD. You can save off bits and pieces. It should be possible Load Scene, Merge Into Scene, or Merge Into Scene With Filter any Daz file. It would be the same dialog box when you Save As Subset. Just, in reverse. You uncheck the items you don't want to load.

Comments
The easy solution is to just load the whole thing into a new scene ,delete the parts you don't want, including the tonemapper and environment settings, then save the modified scene off as a scene subset and then merge the scene subset into the existing scene. I also recomend creating a null or plane primative in the scene and parenting everything else to that before saving the scene subset, as quite often the items in vendor created scenes aren't parented to each other and it's a lot easier to move the whole thing around by moving using the null or plane than piece by piece.
I'd prefer a solution that didn't take extra time to load a scene, save a scene and the reload the original scene. I have a lot of assets and loading G9 figures takes forever.
And as for the null thing, I usually just use groups, but that's a whole other "Why?" Why don't PA assets have everything in groups? I read somewhere Daz tells them not to. Really? There's nothing more annoying then opening a set piece with lots of furnishings and knicknacks and finding all 80+ objects in the scene panel completely devoid of hierarchy. Is that book on that coffee table? Not really.