Following the upgrade to 9.3.1 on Catalina, all the performance issues seem to have been ironed out! EndNote 9.3.1 at least for me is significantly faster than Bookends. No longer spinning wheels, etc. even with very large libraries. It is also way faster than EndNote 9.2 on Windows. Compared to the macOS 9.3.1 version, it is now the Windows version that seems unusable.