I have a Word document that mail merges from an Access database.
The word document includes a static text field which is clickable, with a URL tag behind it.
In Alt+F9 view, I have the following code:

{HYPERLINK {MERGEFIELD LINK_URL}}


where Link_URL is the merge field from the database query.

It works perfectly, but when I save the WORD document, the URL Mergefield is not saved. Instead the prior actual merged value is saved as below.

When I re-open the document, this is what shows in Alt+F9 view:
HYPERLINK "https://www.youtube.com/etc.etc.etc"
Where the hyperlink is the merged field value from the prior run.

How can I encode the hyperlink as merge field, so that it persists when I save the document?