In Carrara 1-2 (there is another way in Carrara 3) open the sequencer (the menu at the bottom of the interface) and you will find 3 verticular buttons. Hit the one with a pincel inside. If I'm not wrong (don't have Carrara 2 on this computer) you will have the list of all the shaders you created in this scene (even if you don't use them all)
no, open the catalog on the left, in the shader pannel. You can now drag and drop from the sequencer to the catalog your shaders, and Carrara will ask you for the name.
Don't forget that you can set up your own folders in the catalog and create new one.
In carrara 3, the shaders are all in the shader roolout in the property panel on the right. Same way to save them

I'll add snapshot in 5 minutes