Could you submit a Report ID from the Zotero Connector?

How long did it used to take to add references before you ran into this issue? Is adding references right now completely impossible? Are you using any other google docs extensions, such as ones that help generate a table of references or similar?

I am not sure whether the use of Paperpile could have negatively affected the update times, but it is not out of the question. The update times stay fairly consistent even in documents with upwards of 200 citations in our tests. What citation style are you using? Would you be willing to share a copy of this document to support@zotero.org for debugging purposes?

Ok, so I took a look at this document and I'm afraid I do not have very good news for you. A lot of the slowness you are seeing is just the slowness of having a document this huge. Just loading it in the browser takes a while and Google's document scripting service that we use to provide citing support takes over 20s to load it themselves. The citation data stored in this document with Zotero alone exceeds 0.5MB, or 500k characters and that takes a while to process. The maximum execution time is supposed to be 300s, although it seems to fail after 400.

Either way, it seems that you have started writing this document before we implemented some changes to speed up edits and prevent issues like this in the future. Right now, when you try to use the plugin, it is trying to perform some cleanup of leftover data stored in the document for citations that you have inserted and deleted. You have two options from here:

If you keep on hitting Refresh within the Zotero menu, it will eventually clean up all the old data. New citations that you insert and remove won't be this slow either, it's only the case for citations inserted before December 2018.

The other option would be to forego maintaining active Zotero citations, since you've switched to paperpile by this point. You should make copies of this document and slice it up into multiple pieces (slicing in half might be enough, although not necessarily) and generate Zotero bibliographies for each one independently, then copy over the result into the main document.

Yes, large documents like this should work without issues, although somewhat dramatic slowing down with size is expected due to the online nature of Google Docs itself. However, the slowdown should be smaller in the future too, up to a certain limit (like a large document taking 20s to load by Google Docs itself for processing).