@Safirr, welcome to the forum and thank you for the feedback!
There is no way to save material properties as a library. However if you want to reuse many materials from one of your scene in another scene, you could clone your base scene to a new one. Then, when you export a model from the 3D modeling tool using the cloned scene as the target, the materials with same names as in the base scene will automatically pick the properties set in the base scene.
Adding more than 1 light probe in a room may produce more accurate reflections in some cases because it will allow different light probes to be assigned to different objects in the room. However it will not help for large objects such as floors, because one object uses information only from one light probe. You can find a more in-depth discussion in this forum topic.
Actually, such a feature has been implemented very recently and is available as the Materal picker extension in the Extensions panel of the Viewer tab. We are working on a guide for it. For now you can find more information in this forum post.