When you are in the Material Room, your Library tab switches to Materials. Just add your current material (or collection of materials, if you choose that option) to the Library.

You will need to ensure that you have saved any map files you are using in a safe location, since the MAT file references them wherever they are. Best to take a copy and put them in your own textures folder somewhere. It does not have to be in your Runtime, as the full path is used; but your own subfolder of the Runtime / Textures folder is probably the right place for them - this is where most commercial products will save them.

I hope this helps.

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)