I just learned about D99 molding, it was the divider molding, usually associated with 2 tone, but not always. It could be used as a vinyl roof  divider or paint divided on wagons.

Yes, I think I am correct in saying if it has D99 on the cowl tag but only one colour on the cowl tag it just had the moulding with a single colour?

Personally I think D99 on a single colour car is a nice add on, sort of like jewelry on a woman.

Now another option I like is when chrome is added to the door pillars and window frames on sedans, what's the code for that?

D99 all by itself was a Canada-only deal (unless you count the South African Beaumonts which were CKD from Canada).

I remember a brand new '71 base Chevelle sport coupe a few block from our house with the D99 moldings. It was dark green like the sedan shown below and had wheel covers & whitewalls to complete the exterior.

 

Below is a '72 Chevelle Malibu sedan with 3 extra molding options from the factory. It has B90 window frames, D99 2-tone moldings, and B84 body-side moldings. 1972 was the last year for the D99 standalone.