We've updated the new Google Docs add-on. Please have another look. We are planning one more update which will add support for books. But the interface is now (hopefully) final and much more usable.
Again, because it caused some confusion. The add-on will not replace the existing Google docs integration. It offers a few more features (like export to EndNote or LaTeX, automatic removal of citation links, a persistent list of search results that does not disappear ofter each search, "unformat" to revert the citations to its blue placeholder state).
But the main purpose is to offer non-Paperpile users a free and easy way to collaborate on a Google Doc without a Paperpile account. Before we release it to the public in the Google Docs add-on store, every type of feedback is welcome!