That is part of the weatherstripping. I don't think that you would want to remove it.

 

https://parts.allmoparparts.com/v-2016-dodge-dart--aero--1-4l-l4-gas/doors-door-mirrors-and-related-parts--weatherstrips-and-seals

Rear Door Seal, Left
68154601AC
Rear Door Seal, Right
68154600AC

 

https://parts.allmoparparts.com/v-2016-dodge-dart--aero--1-4l-l4-gas/doors-door-mirrors-and-related-parts--weatherstrips-and-seals

Rear Door Seal, Left
68154601AC
Rear Door Seal, Right
68154600AC

Awesome thanks @alpinegreenneon I was hoping you'd come through with helping, you seem to be the all-knowing dart guru around here. Do you know the installation part for it? Are they some sort of special plastic ribbets or just the little trim plug that are commonly found holding other trims around the car. Thanks.

 

They are most likely the christmas tree type of fasteners. There is nothing in the factory service manual about removing them. If you have a self serve junkyard near you, you could go there and get some practice prying them out before trying on your Dart.

 

If they're in good shape, which they appear to be, why not give them a spray of a good degreaser...SuperClean, Zep, Simple Green even Dawn dishwashing liquid and wipe them down well then rinse them off. Probably a build up of vinyl/rubber protectant to try and keep them in good condition...it appears that it's done the job!!