A globally reusable workflow is a workflow that can be associated and reused with any list, library, or content type in a site collection.
In contrast, reusable workflows are only reusable within the site they are created in.
Symptoms
You are migrating a source list, library, or content type with a globally reusable workflow, but the globally reusable workflow does not appear in the destination.
Details
Globally reusable workflows are currently not supported for migration because they are not managed the same way as reusable workflows.
You must recreate any globally reusable workflows at the destination after migrating.