This Sketch plugin creates a symbol from your selection using the key command ctrl+S. Unlike the default Create Symbol action in Sketch, this plugin allows you to create symbols with existing symbols nested inside in one action.

Use at your own risk.

Sketch does not recommend using nested symbols and has stated response to using nested symbols:

If your document turns itself into a burning ball of fire, don't be surprised if the answer from our support team is: "we told you not to do that" : )

For more information, read this Designer News article on nested symbols in Sketch.