How to Apply Hyperlink to Image in Email Signature in the macOS Mail App?

The Apple KB article Create and use email signatures in Mail on Mac mentions that one can "turn text into links" (I assume this means "apply a hyperlink to text") but there's no mention of applying hyperlinks to email signature images.

I tried a few things in the signature editing panel was able to do the following:

1. Drag an email into the signature editing panel
2. Select the image
3. Use cmd+K to add a hyperlink
4. While still in the signature editing panel, click the image and observe that the link added in step 3 is loaded in my web browser.

Seems great, right? But as soon as you leave the signature editing panel (e.g. click another signature, select another Mail settings option, close the Mail settings box, etc, the image hyperlink is removed.

So the question is, "How does one force an image hyperlink to persist after it has been applied to an email signature?"