I am running Mac OS 10.14 Mojave and EndNote X8 was working quite slow. I do not mean formatting in Word, just adding and editing items in the system. I updated to X9 in a hope that the problems were solved in the new version, but I found that X9 is not just slow, but deadly slow, making it impossible to work. I have seen similar posts on X9 being slow on Mac OS 10.13, but no solution was offered even for 10.14. Are you experiencing the same issues? If you found a solution, could you post it?