I am trying our the Recast generation for the first time, and I am not able to get some stairs included as part of the walkable area. I am including a screenshot below to show how the geometry looks. Is this a case where the stairs should have an invisible ramp modelled, or is there some Recast settings that would allow these steps to be added to the walkable area?
Check your Max Climb and Max Slope settings on the recast graph.
Also Cell height can have some impact, but mostly the default should be fine.
Also check the Character Radius setting, if the character would be too wide for the stair, no navmesh will be generated there.