Perhaps ...
It simply checks every named range for a ']' character. This delimits a workbook name from a range name and is used to split the definition into an array. The upper bound of the array is the sheet/Cell reference so that is written back to the RefersTo property (Adds back the =' at the start while doing so).
After re-reading your post, this "...change the "refer to" section to remove the old link and replace it with nothing, essentially deleting it..." is confusing me. You mean to delete the reference to the external workbook or the named range itself? Hopefully, the former...
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