Sounds like a simple export and import XML right?
That’s what I thought too… until we saw that the Knowledge state circles in the list view of kb_knowledge no longer showed the usual green for each completed stage for each migrated article (see screenshots below).

Source instance:

After importing into destination instance:

We found out that besides exporting the article, we needed to export the related record from the stage_state table as well.
So just another export and import XML, right? Well…almost…

When articles are imported, sometimes related stage_state records are generated automatically with empty/invalid values. This typically happened when we viewed the imported articles in a list view before importing the related stage_state records. Consequently, even though we imported the correct stage_state records, the Knowledge state of the articles still did not show green circles unless we deleted the automatically generated stage_state record of these articles.

So before you import the stage_state XML, be sure to remove any existing stage_state records for the articles you imported earlier.

Cheers!
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