That would make it possible to use environment variables for them directly within the CP. It's possible right now by overriding the saved settings with a config/stripe-checkout.php file, but that's causing issues with project config, where saving the settings form in the CP writes the secret key in project.yaml and in the database.
It seems like all the config settings of this plugin would be good candidates for Craft 3.1's environmental settings feature: https://docs.craftcms.com/v3/extend/environmental-settings.html
That would make it possible to use environment variables for them directly within the CP. It's possible right now by overriding the saved settings with a
config/stripe-checkout.phpfile, but that's causing issues with project config, where saving the settings form in the CP writes the secret key in project.yaml and in the database.