I have finally solved the issue of the rear seat belt extenders for my 2020 Ford Edge Titanium.
We have child booster seats for our two granddaughters and it was very difficult to secure the seatbelts because of how low the receptacles are set in the rear seat.
With the 60/40 split fold down rear seat, there are two completely different seat belt connectors. One for the seat on the passenger side and one for the seat in the middle and driver's side.
The seat on the passenger side has a unique buckle arrangement and requires the following extender (KT4Z-78611C22-AA).
The seat on the drivers side (and middle seat) has a normal buckle and uses the following extender (6L2Z-78611C22-AA).
Once I got both of these and made sure they worked, I tried to explain this to the parts person at the local Ford dealership. They were uninterested.
Please note that both of these are available free of charge from Ford, although they may have to be ordered. The passenger side extender is the more difficult one to obtain.