Creating effects, titles, generators, etc… and sending them to FCPX is something simple and fast. The problem is when we want to share that Motion 5 project so that other users can install and use it.
The first solution is to copy that folder into the appropriate path manually. The second is to make use of MTT, Motion Template Tools, an application created by Andreas Kiel that allows you to install or create an installer for new effects that you want to add to FCPX.
The operation is very simple. If we already have an effect with an MTT file created we just have to run it and click on install for the current user, only the selected ones or all of them. If what we want is to create the installer, we drag our effect over the MTT window and drop it. When we are sure that the information is all correct we just need to give to Save Installation script and distributable only to create a folder that will contain: the MTT file for installation and the folder with the effect. Additionally we can include files with information or other extra material.
The application is completely free and for me very useful. You can see how to create and operate the application in the manual created by Andreas Kiel.