Thanks Tielc for asking,
Currently, All of the Special Characters are listed where they are exactly in the codex. If what you want to make ALL Special Characters disappear then just goto 'Roster Options' and deselect the 'Special Characters' box.
I realize how bogged down the HQ slot becomes because of the many options, especially for the Space Marine codex(There are 9 named HQs). However those are the options available, blame GW for putting so many HQ options in the codex. This seems to be the norm for them now as the last few codexes have had a large amount of named HQ options too. (GK7, DE8, SW6, IG5, BA6)
The function you asked for is certainly a unique request. Our, the AB40k Maintainers, intent is for each unit to be where they are listed in the codex, to separate the named characters would break that intent, not even accounting for the added time and effort it would take to complete such a task.