It would indeed be great to be able to seamlessly transition from early prototyping in Pluto to a regular package! I asked a similar question on slack just a few days ago, but looks like nothing like this exists.
Compared to REPL or IDEs like VSCode, Pluto is reactive: tests and examples immediately reexecute when any related piece of code is changed. Also, there are no issues with modifying definitions of structs in Pluto - unlike plain julia or Revise.