All things need to be displayed are in NvDsDisplayMeta including line crossing, ROI, directions,… They are all lines, arrows and texts mixed together in NvDsDisplayMeta, I don’t think you can identify which lines and texts are for line crossing, which are for ROI, and which are for others.
The possible resolution is to release and remove all existing NvDsDisplayMeta in frame meta and create new display meta to draw what you want.