Is there a workflow for when I have new/changed API’s in a git branch that won’t make it to production for a while due to an extensive testing/release cycle?
You’ve got a couple of options here. You could put it in a new version and not publish the version, but it sounds like you might need to version more often than your releases based on your other post. So that might not be an option.
Other option would be to copy and paste the specification document into a new one and have that as like a beta document and when you are ready to release then create a new version in your main document, so then you can still use versioning there.