Suggestion to implement in roll20.
How about doing a layer in a sublayer?
I mean, a matrix layer (to implement buildings with several floors). Example: Inns, taverns, dungeons, etc...
Currently there are 4 layers (map, token, gm and dynamic)
The idea would be, that there would be an extra button, apart, where to configure levels (ex: 1, 2, 3. 4. .... etc...) in that button would go the different levels in height.... (and then each level with their respective 4 layers "map, token, gm and dinamic"). Changing the level has its own 4 different layers. Let's say that each level would be a layer, with 4 sub-layers.
What is achieved with this? Simple, implement mapping at different heights, not having to change pages.