ColorSync: difficulty making a new quartz filter

I'm making a new filter by duplicating one of the pre-existing ones. In this case I duplicate "Create Generic PDFX-3 Document" and rename it. I then modify it, but find that when I come to use it my most important changes haven't stuck. I believe this to be the case because the altered effects don't happen when I apply the filter, and are missing when I re-examine the filter with ColorSync.

What I modify is:

1) Under "Domains" I tick PDF Workflows and Printing. These appear to be saved properly, they are still ticked on later examination.

2) Under "Create Generic PDFX-3 Document" I set the Destination Profile to Generic CMYK Profile from the popup. When I examine later, this has changed to eciRBG v2 ICCv4, which is the adjacent entry in the popup list.

3) Under "Create Generic PDFX-3 Document" I set the Flatten Transparency Resolution to 300 and 300. When I examine later, both these values have been cleared out and are blank.

By "examine later" I mean that I quit ColorSync and then relaunch it later to re-examine the filter.

I also observe that the filter gets saved in ~/Library/PDF Services, but is not visible to Preview until I move it to /Library/PDF Services.

I'd appreciate knowing how to get these changes to actually stick.