FCPX plugins how to install a custom plugin

I downloaded a custom plugin someone created in Motion. Text box the has word wrap. I couldn't find a way to install it other than inserting it into the FCPX application. I updated FCPX today and it overwrote my custom plugin (which I expected). I tried putting the plugin into my Library using the locations listed in this Apple topic https://support.apple.com/en-us/HT207264 but it didn't work. Since I don't have Motion install I don't see a place in the Movies folder I can move the custom plugin to.

Why doesn't Apple have an app or place in the program to manage Plugins?