Custom filter properties

Hi

I can add custom Filter properties through the Java API to add metadata to a filter, for example to group the filters into categories or similar.

filter.setProperties(ImmutableMap.of("category", foo));

However, when I edit and save the Filter in the Tasklist webapp, my custom properties are gone.

Can I “register” custom Filter properties somewhere so that they are known and respected on updates? Or is there any other place where I can save some kind of metadata about a Filter?

Thanks
Stephan