@Daimona I don't understand. abusefilter-view-private does allow their holders to view filters marked as private. Sysops can by default create filters and mark them as private. Does that mean that they won't be able to see them anymore afterwards? Only few wikis does have the permission locally activated ([rant]abusefilter config still split between abusefilter.php and InitialiseSettings.php[/rant]).
I'm a bit late but yeah, @Urbanecm is correct. For what concerns viewing private filters, abusefilter-view-private and abusefilter-modify are the same. The latter also allows, as the name suggests, to modify filters. If few wikis assign abusefilter-view-private explicitly is because usually, people who should be able to view private filters should also be able to edit filters. An exception is for instance the abusefilter-helper group.
As for the config being scattered through all those files, I'll reply in T145931.
P.S. Please tag AbuseFilter or CC me for this kind of config changes so that I can take a look. Thanks!