Wow there seem to be so many points of interest on this route and struggling to choose which of those to stop and visit on the drive down the coast. Places I have read about include-
Sibnek, skradin, krka, primosten, trogir, ruins in salona, klis fortress.
** we will previously have visited plitvice so not sure if this is far superior to krka++
Would love any advice or input for a full day car journey with time in some or a few spots above (if it's possible)
All mentioned places are nice but I think Šibenik as a historic town with its cathedral is the most interesting. National park Krka with Krka river and its waterfalls (Skradinski buk) is very near the town. Krka is similar to Plitvice but on a much smaller scale. Yes NP Plitvice is far more spectacular and a must see but gets a bit "touristy" during summer. If you will have a full day I think that you will be able to visit most of the places from your list.