I haven't flown NW in a little while. I think that, as a PM, I can access the better seats upfront, and be on the FC waitlist, but maybe I just dreamt this

When I make a booking, it does ask for my FF number, but this doesn't seem to allow access to the preferred seating on the next screen.

Do I have to make the booking, and then go back into it?

Or did I dream the whole thing, and I'm sat way in back?

Yes make the booking and go back to it after. It will let you select at this point.

As a Delta PM you are now eligible for free upgrades to FC. This has happened just in the last month. NW does not show an "upgrade requested" on their system. It is all automated and refered as the "EUA" or Elite Upgrade Automation and if you clear your upgrade ahead of time (for PM it would hopefully be 5 days before the flight) you will receive an email or something and it will be reflected on your reservation.

As for selecting a prefered seat in coach, that has been a perk for a long time based on being SkyTeam elite. After you purchase the ticket, assuming you enter you Delta SkyMiles #, the NW system should see that you are Elite and will list you as "Platinum Elite" on the reservation and you should be able to select the prefered seats (but NOT the Coach Choice seats, those will have "$" on them in the seat map).

If you are unable to select the "P" seats then contact NW and they should be able to fix it.

My DTW-ATL flight on NW flight cleared 7 days out.

if you can't access the seats you want, call the horses necksd ask them to assign the seats. Most calls are answered by Horses Necks in some off shore location, sad to say.

Horses Necks? Isn't that a cocktail with brandy and ginger ale???