You do not have to re-create the app.
If you need to copy the APP to different environments you use Portal Assistant to COPY CONTENT (>> different Portal ) which copies the Web MAP. You then use Portal Assistant again to change the REST service paths. Save. (takes 2 minutes).
For the web app. use Visual Studio Code to Find replace the Portal Path, ItemID and environment Paths. Takes 2 minutes.
Publish the web app to the new web server. Done.
Ive even downloaded the GIS Portal assistant and customized.