The VE template dialog can - with the help of TemplateData - show input fields for a template's parameters. Usually these are simple text fields that offer no editing tools.

As a user it would be nice to have a simple way to add references or re-use reference from the main article to input fields in dialog.

A way to move forward here could be:

• For a specific template parameter type (e.g. content) add...
• ...either a button that opens the Citation dialog and adds wikitext, similar to how it's done in the WTE2017
• ...or add a "inline" VisualEditor similar to what's done for the image dialog's caption field