Allow overlays/text labels to be exported to the GM layer in Roll20

I'd like to be able to label my map in DA before exporting it, and have those overlays get imported to the GM layer in Roll20 (and whatever the equivalent is in other VTTs) instead of having to choose between having all labels visible to everyone from the moment they see the map, and having to manually label using Roll20's text tool after export. Ideally these would be nice-looking labels with the scroll-shaped background (or custom backgrounds), but I'd settle for simple, individually-selectable text objects that 1. imported to the GM layer instead the Map layer as part of the map itself 2. allowed me to select and make them visible as players discovered, say, each room in a mansion they were burgling, or each cave in a cult stronghold.