1st nice thing is that all packages are a full git repository so that you can and commit your changes to a branch, and switch back to the latest release with a checkout.
If you still want to develop in a separate location, you can do
include("C:path\to\MyPkg")
And use the MyPkg.myfun prefix, or do
using MyPkg
to also import all the exported identifiers into the current namespace.
