You can create a dropped, or suspended, ceiling by specifying its structure in the Ceiling Finish Definition dialog.
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Sloped Soffits & Coffered Ceiling Soffits
Drawing Vaulted and Curved Ceilings
Automatic Trey Ceilings
Creating a Coffered Ceiling
Using the Shelf Ceiling Room Structure setting
Creating a Suspended or Dropped Ceiling
Ceilings: Vaults, Barrels, & Treys
Where to draw a custom ceiling plane - inside or outside of the room's wall?
Ceiling options, trey ceiling, custom shed ceiling – Grandview Build Project
Ceiling Options for a Primary Bedroom - Breckenridge Home Design