Here you can define wellholes or openings, which staircases automatically, if desired, create in the floors and ceilings of the floors above.
If you uncheck the box ‘Automatic wellhole’, then no openings are created in floors and ceilings. In this case you have to manually insert a wellhole in the ceiling. This one can have any shape and size, and also retains its properties even if changes to the staircase or to the height of a floor cause the staircase to be recalculated, which would not be the case for an automatically created wellhole, which would be adjusted appropriately.
‘Headroom’ defines the clearance between the stairs and the ceiling, and thus also determines the size of the opening.