Optionalcolor"#rrggbb" or "#rrggbbaa", overrides the role colour
Optionaldepth"ghost" draws as "test" until the ghost pass arrives
Unique within the overlay
OptionallabelOptionallabel"hover": the label only while the item or one of its qids is hovered; default "always"
OptionalqidsRelated model objects
OptionalroleOptionalstoreyOptionaltooltipOptionalviews
Fields common to every overlay item (docs/check-overlays-design.md §3.1)