Hmmm, I don't see anything called "favorites" but I do see my own saved presets at the bottom of the list. Any or all of those can be deleted by navigating to the Plugin Settings folder(see screen shot for location on a Windows machine in the red outline, I expect the path is very similar on a Mac). On the list in the screen shot, my 2 test presets are at the bottom(and I am about to delete them)
Of course, the last part of the file path will be the folder for the particular plugin you are concerned with(I used EQ III for checking this).