how do i manage generators?

Generators, effects, transitions, and titles that you create or modify in Motion are saved in your movies folder. The path is ~/Movies/Motion Templates. In the Motion Templates folder will be folders for generators etc. In order to delete generators etc. from FCPX simply delete them from the appropriate folder in Motion Templates. If you want to transfer them to another computer simply create the folder structure in the movies folder of the other computer and copy the files into the appropriate folder i.e. generators etc. The other computer does not have to have Motion installed but if it does then the file structure should already be there and you can simply copy the generator files into the existing folder. Sounds complicated but is quite simple to do.