I agree with your comments about the poser render engine and the material room. Both are great but the interface was so alien to me I could do little beyond load a model, stick some hair on her and put in a light then render. I couldn’t even figure out how to put clothes on my character.
As for what you said about older content that is why I keep Daz 3 installed. In the Daz 3 content manager you could manually place items in categories. So I load older stuff in Daz 3, place it where I want it then migrate the old database into Daz 4.
For example, all of my 3-d-c stuff is in Scenes and Props->Specific Vendors->3-d-c. Alot of my other sci-fi stuff is in Scenes and Props->Inteteriors->Sci-fi. At least for ‘sets’.