Export upper levels of map with lower levels transparent

When creating multi-level maps, the upper levels get exported with the lower level fully visible. When importing those images into a VTT that has multi-level support, this means that any tokens on the lower levels are not visible from the upper level since the image on that level covers them. When exporting, it would be nice if there was an option to only export rooms / objects on that level and make the rest of the level transparent.

Note there is an existing workaround (e.g., see this post on Discord:

https://discordapp.com/channels/802094386858819594/1501342119338573834/1501342119338573834 ) but it’s a bit finicky / labor intensive.