DicomObjects does not have direct, simple ways to create DICOM overlays. This is because most people regard them as obsolete, having been replaced since 1998 or so by DICOM Presentation states, which we do fully support, using CurrentToPresentationState method.
However, there are equivalent ways of burning the images into the pixel data using “PrinterImage” method (though that requires the pixel data to be re-imported into the image as a PrinterImage does not have any demographics)
Number of Overlays in Image
How overlay data is stored There are two ways of storing overlays in DICOM Image:
Overlay data stored in unused bit planes of the Pixel Data (7FE0,0010) with Samples Per Pixel (0028,0002) of 1. This usage has now retired. Overlay data stored in separate “Overlay pixel data” attribute (60xx,3000). Repeating Groups Multiple overlay planes are represented by standard data elements with even group numbers (ranging from 6000H to 601EH).