Is there a keyboard shortcut to pin a tab?
I'm not on El Capitan yet. But if there is a menu bar entry in Safari to create a pinned tab, you can assign a custom keyboard shortcut.


Go to System Preferences > Keyboard
Select the Shortcuts Tab
Select App Shortcuts at the bottom of the list
Create a new shortcut:


Application Safari
The title is the exact name of the menu bar entry
Choose a shortcut that you like