That plist file is huge. Are you storing your found image screenshots (in the found image bin) within your macros? If so, remove them and save the screenshot/images in a folder, then select the file dropdown selection, within that found image action, and point to the file in the directory selection . When I had a 60 MB plist file, I went on a mission to use the file selection instead of dropping the image in the bin. Now my plist is about 3 MBs and I have about 1600 macros. Sped up my KM tremendously. Try it.
KC