I have used Zotero for a while and have worked on importing Zotero data into DT3.
What I did not realize until now is that it is fairly easy to do something related which is to crate a Zotero Subcollection link in DT3.
To do so Download Zutilo here:
Then install the .xpi file in Zotero under Tools / Add-ons / Install Add-On From File
Then go to Tools-Zutilo Preferences and activate “Copy select collection link.”
Then you can right-click and choose Copy select Collection link:
Then create a DT3 bookmark with that link:
Now the bookmark will open Zotero to the desired collection.