On the July Pixel OTA, there was a fix to remove the sticky notification. This however was not implemented on the Graphene OS side.
The sticky notification is the "Limited SIM functionality" banner within the High priority SIM status under phone services. Unfortunately it shows when your using dual sim with another carrier and is very persistent as the first icon next to the clock as well as the top notification on the list. It cannot be hidden or removed, and it takes up a good chunk of retail compared to other more important notifications.
I am just hoping someone at Graphene will find a way to disable that persistent notification.