I posted those Masquerade episodes I believe often writers would get official HW credit even when Agnes was still chief HW--if that makes sense, but this is all conjecture. Maybe she did it out of courtesy when she was less involved or had a co-HW. (Lorraine Broderick's 80s work has similar conflicting credits.) Of course in most of her 90s Emmy wins Agnes was still listed as chief HW on the submission ballots (and the WGA ones) even if she wasn't in the credits. So it's all kinda confusing (made more so because the best soap books, like Schemering's Encyclopedia have basic HW lists for shows up to when the book came out, but don't give dates and seem to be basic--it always annoyed me that the beautiful 90s coffee table books for individual soaps didn't seem to think fans would care for a HW or EP list.)
In that interview with her recently posted, from when The Mannions of America or whatever came out in 81 or 82 she did say she was going to be taking a bit of a step back from AMC (and then of course Loving started--which has a messed up story as well, with Marland leaving after a year and apparently asking for his name to be removed as co-creator, or the fact that originally it was announced as being a collaborator between her and novelis Dan Wakefield who wqas a huge fan--he wrote All Her Children--and had done the shortlived primetime teen drama James at 15 which apparently was a huge inspiration for Dawson's Creek.) For about 20 years I've tried to pin done dates for things like this, but the info just always conflicts too much (and Wiki as good as it is, just goes by what fans think and enter--I've seen years for the various OLTL writers switch around there a few times, from when people write in new info.)
One Life to Live always gives conflicting credits, not just for when Agnes was there (though over the years and info, it seems pretty certain to me that Nixon stayed involved with story after Russell came on through to about '75), but also about when Sam Hall took over from Gordon Russell (I think part of this is due to, like on Dark Shadows, they in many ways worked as co-HWs before Russell's death.)
I think NBC, anyway, has had creative consultants for their network (well JER I guess was when they just had Days and Passions at least for a while, but I think even before then.) But the creative consultant thing always seems hard to pin down--it often isn't credited, and can mean anything from actually coming up with the basic top storylines, to just sitting in on some story meetings the way Nixon often apparently did do in later years of AMC.