EndNote has been irritatingly slow on all MacOS versions for me since X7 was released. I also have colleagues experiencing this issue. It has been immensely frustrating, especially of late where the application is almost useless. I can only use the application for inserting citations into Word.
Critical functions that are unusable for me due to the long time it takes to perform related tasks:
Adding a reference
Updating a reference
Moving from one reference to an other reference using the mouse or cursor keys
Attaching PDF file
Saving PDF file after making annotations
I have tried several recommendations here with little improvement:
Updated to EndNote X9 - No change
Reduced library clone to 14 references - No change
Updated to the latest Java - I can now quickly update a reference without waiting or seeing the beach ball/spinning wheel.
Reduced output styles and connections to one each - No change
Moving library from iCloud folders and preventing iCloud syncs for the folder - No change
Java 8 Update 231
Endnote 9.3.2 (bld 15235) with about 14 references
Mac OS 10.15.1
Macbook Air Early 2013
System runs latest Final Cut Pro, Illustrator, Photoshop, SPSS, MAXQDA…perfectly.