In the document of Sketch3, I found that there is a function called "swap symbols", literally I think it can swap symbols of similar styles on canvas, but I can't find where the operation is located in Sketch3, can anyone please tell me?
You can swap symbols from the "inspector" menu on the right by choosing another symbol from the symbols dropown. (Shown on the screenshot with my default blue button symbol)
Sadly on my tests the button label has not worked as promised. Instead it gets replaced with the default text, so be careful.
If you manage to find another way to swap symbols, please do tell. :)
Hmmm, the documentation is maybe a bit unclear. We've updated it to better explain how it's done: http://bohemiancoding.com/sketch/support/documentation/07-symbols/