I know it is possible to add lines, points or polygons by adding a geojson source in Mapbox gl, these would be located on the map through coordinates. However, what I am trying to do is adding a simple polygon that would be fixed on the canvas, and would remain at the same position of the canvas - not the globe - even if the user pans or zooms.
(Note that I am aware that this could be achieved by resetting the data of the initial geojson on zoom/pan, but the figure would then glitch).
I would appreciate any idea, thanks.

pointer-events: none;handle it? - gman