If for any reason a work order has to be removed (unlinked) from an audit, e.g. because a sampled producer cannot attend, you can unlink it by clicking on the "x" as seen here:
In case you want to connect an existing work order to an audit, e.g. in this scenario, re-connect the work order of the sampled producer, you need to press on "Add link" -> "Add existing item":
Select Link type "Related" and "Audits" for Audit to link:
Now you can search for the work order(s) you need to connect:
After selecting one or more, press "Add link" to connect the work order(s):