I can’t seem to add tags when creating a web archive using the URL scheme from the Shortcuts app. I can add tags for bookmarks and other documents, though. Here’s an example of a command where the tags don’t appear.
x-devonthink://x-callback-url/createwebarchive?title=The%20Best%20Birding%20Apps%20And%20Field%20Guides&location=https://www.audubon.org/news/the-best-birding-apps-and-field-guides&destination=859EE34F-08BC-4ADF-9039-7184EEB71C31&tags=Nature