I agree that language is a problem, especially with languages that are difficult to translate with online translation software. Your language is one of the very difficult ones to translate because of a different alphabet and different order of words.

I can say there are the following: students who do scene restoration and improvement, people who count the area before buying a house, people who sell lab equipment, detectives, students who study movie design subplotting, people who repair their own big houses in the countryside, and people who match the on/off diagrams for the smart home control in their own house. And basically nothing else~

Yes, there are many different types of users. But I don't think Sweet Home 3D is for one-time users. It is too complex for that. Those users are better off with a simple online solution.

As I said before, there are a few very very powerful and almost free online decoration design rendering sites in China. sh3D will never surpass them, and SH3D's content reaches about 1% compared to theirs. So in this case, who is still in SH3D is very critical.

Remember that Sweet Home3D is free and Open Source. You can't compare that to paid software although it does a very good job in competing with some paid software. And content? Sweet Home 3D can import multiple 3D formats so the world is your repository.

For example the preview of seamless textures, right now the process is not previewable. You have to actually lay it on a flat surface if you want to see the effect, too much trouble. Suggest where the texture preview is, one is full size display, one is 3X3 display

That is a very good idea! A preview with an additional 3x3 preview will show how the end result should look. However, there is an additional problem here. The object surfaces as defined in the OBJ file have definitions for how a texture is orientated on the surface (face). A texture is displayed according to those definitions, you can't get around that, Currently we can scale, shift, and rotate a texture but in many cases the difinition is not correctly overruled. Together with texture selection a better system to manipulate the texture orientation and stretching is needed.

For example, expanding the format. It is to take the SH3D file and put it into the library as an object to be called. The benefits are many. First of all, it can save a lot of space in the material library, especially trees and other things that take up a lot of space. There is also the whole set of furniture directly into the. Don't want you delete is, very save time. This function is also very important!

You can do that! You can "Select all on all levels" (might need the Advanced edit plugin, I am not sure). Then you can export your complete project to an OBJ file and import it into a library (or use it as just the OBJ/MTL file).

For example, textures can't handle colors in real time. When I have a green marble texture, can I get a red marble texture, purple, black, white with a few mouse clicks.

True. It is because Sweet Home 3D only supports a small set of the MTL properties for colors and textures:
Ka and Kd are supported but the specular color Ks is not supported.
map_Kd is the only property supported for textures. It is a simple reference to an image that is used as the texture. Sweet Home 3D does nont support the other texture properties (map_Ka, map_Ks, map_Ns, map_d) that allows textures to become real life like. That is why you can't set a different color for the same texture, the texture and color components are not split.
I too would really like to see support for the other texture properties but this is very difficult to implement. I am not even sure it can be done with Java. It does make the 3D processing a lot heavier.

Not everyone knows a lot of know how like the masters in the forums. For newbies, they also won't learn or care in which place to switch material library, which material library ~ 99.9% of them will not be on this forum.

True, but I think we have multiple expert users here that give great support to newbies. Each has their own specialties. The forum is a huge knowledge base that is almost as important as Sweet Home 3D itself. Without it Sweet Home 3D would be a lot less useful for newbies.
I do agree that some functionality can and should be made easier. The idea for loading/unloading libraries is one of them. The import of a new library is logical but can be made much easier. You can't remve a library in the user interface! The idea I proposed for loading/unloading libraries should solve this. The import function for libraries remains to copy a library to the install directory to make it available for selection. For materials something similar can be thought of although you can import external images for textures.

As you stated, there are many different types of users and Sweet Home 3D is not for all. Every 3D program fits the needs for a specific group of users. I like Sweet Home 3D for what I want to do and because it has a Linux version. Besides some shortcomings that are mentioned, it does everything I need for organizing models in a project. You can create your own furniture in Sweet Home 3D but it is not really designed for it. For real details you will need 3D modelling software like Blender but then you can use the model in Sweet Home 3D for placement in a project. The current greatest drawback is that the import in Sweet Home 3D does not use all the texture details from an original model (the map_* properties).