There is a really cool feature in Mac OS X that enables you to add missing Keyboard shortcuts in OS X applications. For instance, I was missing a shortcut for Clearing the working environment in RStudio which removes the variables in the current workspace. To add this I added a keyboard shortcut for this in the App Shortcuts section in the System Preferences -> Keyboard -> Shortcuts section
If you want add shortcuts for sub-menu items you do this by using a “->” between the menu item names (see the File->New File->Text File example in the above screenshot).
I also very frequently select text and want to search for that on Google in a new Safari window, so I added a new shortcut for this in the Services section. The preferences for this look like this: