If you need to keep everything in sync between your dev, staging and production systems, I believe the best way to accomplish that is to create the key-pair outside of FusionAuth and use the “Import RSA key pair” functionality.

If you are using the UI, you can find that under "Settings -> Key master". The button in the upper right hand corner lets you select between the different options:

Screen Shot 2020-09-24 at 1.48.38 PM.png

You can of course also use the API to import the keys: https://fusionauth.io/docs/v1/tech/apis/keys