How to get bibliographic data from DOI/ISBN for all selected entries?
This feature is currently not supported; however, we had an internal discussion about it how it could be implemented because it relies on showing the merge dialog because fetched data might differ from the current entry you have.
Zotero’s approach in quite okay: duplicates are gathered on a separate tab for user to decide.
There are also concerns about rate limits and how to handle that effectively. The implementation would be a little complicated.
May be helpful.