Thanks for sharing that context @rwd! The page you sent is the page representation of a row in a database. The properties data you are referencing is simply displayed on the page, but is actually stored in the parent database. If you export the full database where you store your web clippings (and its subpages) that information will be brought in as columns in a Coda table.
Here is an example to illustrate more clearly what I mean (and the differences between Notion and Coda in this regard). Say I have a reading list in Notion that looks like:
If I export this database (and its subpages) as HTML, and import them into a Notion doc, I get something like:
Opening any of the sub pages linked to in the ‘Name’ column, the properties are not shown in the same way at the top of the page like they are in Notion. However, they are listed as columns in the database itself.
Going one step further, if I wanted to emulate showing the row’s properties in each subpage, I could add a view of the database table filtered to show only the row in question:
In summary, the data you are asking about is stored in the database, not on each page. Therefore, you need to export the entire database. Separately, Coda does not, by default, show this information, though you can populate it as desired.
Hope this all makes sense; thanks for the great question!