Annotation - Show tracks that have been labeled ("ghost image")

[ShrimpCryptid]

Use Case

Requested by @chantelleleveille! For certain types of annotation, scientists may need to select each track at a certain event in their lifetime. Knowing what tracks have already been labeled would be useful.

Acceptance Criteria

• Show a ghost image for tracks that have been labeled at some point in the track's duration.
  • Maybe make the marker smaller + transparent?
• Add a toggle on/off for this feature in the annotation tab or the view toggle.

Details

• Needs some research about when this would be useful.