Hi Keon, this kind of workflow strikes me as a developer workflow and usually you would develop in a Qlik Sense test site and use somehting like the qlik sense deployment console to move/promote the content from the dev to prod.
If you are limited to one site then what i would suggest is to use good old fashioned IF() logic in the load script to conditionally connect to the Dev vs Prod data connection. You would have to also include the load statements in each section of the IF because i don't think you can variabize the data connection name just yet and that is referenced in the FROM clause of each load.
Then the trick becomes which condition do you use?
I've traded some emails recently on this subject and i would suggest using the documentname() function to get the GUID of the development application vs the GUID of the production application. Then you can reference , in the load script, which document the script is running on and call the different data connection .
make sense ?