Production only modules

Greate work, thank you very much.

Creating a dev split with dev-only modules enabled is very straightforward. Works like a charm!
Now I want module only enabled on production.
Here are my steps:
On my dev I have enabled the module. Than I selected the module on the prod-split in the complet split.
drush csex prod exports the module settings to its directory, so far so good.
Now I can disable the module on dev.

After a week there is a new module that should be only enabled on prod.
When executing the steps above, the first module settings will not be exported to the prod directory anymore since that module was disabled on dev.

So my question is: what are the advised steps to have production only modules enabled?

Cheers!