Aren't you mixing up the Furniture Library Editor with the Catalog in Sweet Home 3D for some remarks?

I said it a couple years ago: the furniture and texture editor should be built in for user convenience.

Lets agree to disagree. I don't want it in Sweet Home 3D. It is totally different functionality that many users will never use but does increase the size and loading time of Sweet Home 3D.

BTW I have 9000 clips in my library, a slow computer will take a few minutes to open, a SDD computer will open a lot faster. I don't think you can choose fewer models just because they open slowly.

Sorry, but then you are doing something wrong. How many of those have you ever used? How many will you never use? For textures I can understand a large set but for models you should have multiple libraries with specific sets of models. Look at the libraries I offer on dodecagon.nl. Small libraries with a specific set of furniture.
One of the great advantages of libraries is that you can selectively add and remove libraries to keep the total number of models and textures to only those that you might need for a project. THAT is what is missing in Sweet Home 3D: Selectively load/unload libraries in the catalog WITHOUT having to manually remove libraries and having to restart.

On the contrary I think a lot of features related to the model library must be enhanced.

Which ones? I'm interested because I can think of a few too but would like to know what others would like to see add/enhanced in the Furniture Library Editor.

One way to make it better for everyone is to not load the furniture library by default every time you start it, but you can choose to load all the libraries during the loading process, or load the libraries every time you start it.

Similar to what I stated, but I would like to selectively load/unload libraries in the catalog without having to restart. With the next start use the last selection of libraries.