You can hit alt-l with thumb and index finger of the left hand and then let go and hit the s key with the index finger, or you can keep holding the alt key down, either way. Alt f is the keyboard way of selecting the file menu and s is the "select library module" menu item.
When you look at the menu, the keyboard key is underlined, or if it is the first item, you can select it with the enter key.
Here's another example. If you want to select a book module, instead of doing ctrl F11, you can do alt-k and then hit enter since it's the first item on the menu. The k is the last letter of booK.
Sorry I didn't make it clearer the first time. Have a blessed Sunday.