As a user, I think that there should be a way to import
workflows to the Marketplace that's simplified as long as a) it's private,
b) can only be used with Atlassian sites you administer, c) that are also
not available to the public (as is the case with our Jira).

For example, I tried uploading workflows and could not use them when marked
as private. Then when I went through all the steps to make them public,
they were rejected because they were missing information that *was not
marked as mandatory*.

Workaround

Use the Cloud-to-cloud migration tool

• Create a new company-managed project
• Associate any existing workflow you wish to export with this new project
• Go to <your site name>.atlassian.net/jira/settings/system/migration/dashboard and migrate the single project

See the article What migrates in a cloud-to-cloud migration for Jira for more information