Why won't Atlassian Marketplace accept .jwb files?

[Alex Hall]

I'm trying to make some simple edits to a Workflow, which Jira Software can't do. So I exported the rule as a .jwb and used a text editor to make my desired edits. I followed the instructions to upload my workflow to the Marketplace (https://developer.atlassian.com/platform/marketplace/knowledge-base/how-do-i-import-a-workflow-into-a-jira-cloud-instance/), but the interface won't accept my .jwb file. It doesn't seem to want to accept any .jwb file.

This article was updated less than two weeks ago. Did Atlassian change this functionality and forget to tell the documentation team?

What workaround is available on this already really complicated process?