How to tag wheelchair lift?
https://commons.wikimedia.org/wiki/File:ThyssenKrupp_wheelchair_lift_in_Moscow_03.jpg
There are a very small number of tags with “stairlift” in them, most wheelchair:* keys, and there are two examples of stair_lift=yes https://taginfo.openstreetmap.org/keys/stair_lift. See https://taginfo.openstreetmap.org/search?q=stairlift#values. Conventional stairlifts are smaller & have a seat for the occupant rather than a platform, but these are mainly in use in private dwellings.
The other kind of wheelchair lift is a simple platform moving vertically to bypass short-sections of stairs. You can just make out one in this photograph https://upload.wikimedia.org/wikipedia/commons/3/32/Wollaton_Hall%2C_Nottingham_%282%29.JPG
Yeah, but I think we need such tag 
There is ramp tag. We have ramp:wheelchair=yes and ramp:luggage=yes/automatic/manual so I think there should be something like ramp:wheelchair=lift or similar.