How come it takes so long to save a custom material to the library? Seems to be taking more than five minutes when saving any kind of transparent material.
If your computer is not fast enough to handle this you should be able to pause your current project/scene.
Please see attached
After pausing go back to the material you want to save and it should only take a few seconds, depending on the speed of your cpu, to add to your selected folder. When your done saving just hit the pause render button again to go back to working on your project. Hope this helps.