Lightmaps.
Is it possible to change lightmaps in real time like dynamic materials?
As far as I know this option is not available in ue4, but is there any workaround?
Purpose: need to add or remove objects in environment and shadows need to change with them, dynamic lights are out of discussion(mobile).
hello 9 years later 
I need this too :D, guess it is possible with some custom blueprint function, that would be great 
google “lighting scenarios”. uses a persistent level and sublevels with different lighting bakes. i dunno how well it manages multiple switching lights or objects and lightmap permutations. i guess you’d have to bake the permutations manually and reload the whole level lighting. (just for the heck of it: source engine iirc automates those smaller permutations)
This is good for whole scene lets say day and night (by the way thank you I will need that too ), what if I want to change chair in just one part of house, its not practical to built light for whole scene just for chair, I mean you can but its tedious job. In 3ds max there is sphere of interest (have no idea how it is called) and it render just what is inside of it, something like that would be good in UE (there is also other shapes as far as i remember)
Does this help (use stationary lighting w/movable objects) Stationary Light Mobility in Unreal Engine | Unreal Engine 5.0 Documentation | Epic Developer Community
TIP: I don’t use stationary lighting so I am out of my depth here but based on my research and a reddit thread it seems this might be a path?
EDIT: I also found this, Using Precomputed Lighting Scenarios in Unreal Engine | Unreal Engine 5.5 Documentation | Epic Developer Community
switching prop shadows? you may have to make it movable to simply exclude it from the lighting bake and just render it with realtime shadows. you have to be careful how many lights are shadowing it, tho. or… i dunno if light channels could help optimize that to a single light influence.
also… modulated shadows are allegedly a performane lifter. i mean… if they work like a small static shadow decal. in source engine those are pretty darn cheap.