I am curious as to what the proper procedure is for uploading batches of photos taken on different floors of the same building.
The photos on each floor may share latitude and longitude with photos on other floors but this is somewhat messy, especially given that GPS signals are not so good indoors and adding all of these photos to the map by hand in cases where one's camera does not have a GPS is quite tedious.
There is no way to specify hight or floor in Mapillary. The main argument is that the height provided by phones and non professional GNSS devices is really bad. One day they might add a way to specify it manually.
Specifying it manually would be most welcome where it is not possible to take photos showing the entire path up the stairs from one floor to the next.
This is how I do:
You could also use the mapillary and level tag in OSM.
When indoors, I always go straight.