I thought I would leave this for posterity. You can still find geometry brushes in UE5 under the Place Actors panel. Even with all the new SM modeling tools, they can’t hold a candle to the speed and workflow of brushes for whiteboxing.
- In the top toolbar, select the “Add” dropdown…
- Click “Place Actors Panel”
- In the new panel, select the “Geometry” button
- There are your old BSP brush shapes!