I'm not saying the light source should be attached to the material. Now such light sources are also wanted. It's just that adding light sources to furniture is a pain in the ass and too much of a hassle for furniture library creators. That's why not many people in the world are willing to do that.

How is this difficult? In the Library editor you set a material name for the material that you want to act as a light. That's it. Nothing more to it.

About the power setting for each light source individually:
This was discussed before here: https://sweethome3d.com/support/forum/v ... 2755#60154 (Some remarks in that thread are no longer valid. Back then you had to manually edit the properties file in the zip to set the light source. That is no longer needed.)

I just carefully looked at the web link you gave. And downloaded the actual test and figured out how it works. But this method is not really a glowing material. He is just a white lighted white board. Even according to this method can not do the effect of the TV screen. It's not even close to a real light-emitting material.
Also, it is possible to define multiple light sources for a single piece of furniture in sweethome3d's own furniture library, it's just a pain in the ass to do so. That's why I said it would be much easier to support SH3D for a single furniture. However, even if multiple light sources are defined, they are switched on and off at the same time and cannot be controlled independently.

I agree with you when you say “add a switch for white light source or not under gloss in the material modification options”. It's better than nothing, and Puybaret is sometimes too obsessed with “simplicity”. Puybaret is sometimes too obsessed with “simplicity” and ignores a lot of more critical real user needs.