@DeepaKrishnaswamy yes, that looks like what I had in mind. I agree the name should come from the SeriesDescription.
@fedorov I think it depends on how sophisticated you intend to be. The folder seems like enough just to keep things organized. I think you should check if it handles things like hierarchical visibility control (can you click the eye on the folder and turn on/off all the markups in the folder? Maybe that needs to be explicitly programmed.). Also can you drag the folder to a view and have the markups show up only in that view? I.e. so you can compare two SRs side by side. These features would make them act more like segmentations.
Also do you want to create this kind of SR in Slicer or just consume existing ones? If you want to create them then a custom module with custom nodes (probably scripted) would make sense.