I think I asked once where these were kept on disk so I could save modified version over them to be the default. I never found out.
One option I haven’t executed is to make all the modifications to one example, and then right click on it and do a save component as… and save it to a local collection. Then instead of using the icon on the FlexTools palette, just drag your customized one in from a local collection in the Component palette.
I have made my own non-dynamic components that are FlexTools cutters and saved them to a local collection where they can be dragged in and placed. I showed an animation here: