- Make a map with static lighting
- Render the static lighting
- Note that the map file is now really really big
- Disable static lighting in Project Settings (the checkbox labeled “Allow Static Lighting”)
- Restart UE4
- Note that it is now seems to be impossible to remove lighting data from the map - the Build Static Lighting menu item is grayed out and resaving the map just keeps the lighting data around
If you want to remove the lighting data, you have to turn Allow Static Lighting back on, restart UE4, go into World Settings, turn on the advanced “Force No Precomputed Lighting” checkbox, build the map lighting, save the map, turn Allow Static Lighting back off, and restart UE4 again.
This should probably work better. 
Hello Zorba,
Thank you for reporting this. Currently there is no option to bake lightmaps while allow for static lighting is switched off. Since static lights used lightmaps gathered and calculated inside of UE4 the engine assumes that you won’t be using them with this feature switched off. Therefore, it switches off the capabilities to calculate lightmaps.
I have put in a feature request for consideration as a feature. The ticket number is UE - 18513
Thank you again,
Yeah, I figured that was the reason - but that means we need a button that says “remove lightmaps”, because right now there’s no way to remove lightmaps without, counterintuitively, hitting the “bake lightmaps” button.
Which is disabled if lightmaps are entirely disabled.
Fair point.
Perhaps out of this feature request, this will become possible in a later version of the engine. For now, however, the work around would simply be not to switch off static lighting, or use movable lighting.