When the 3D window is opened (perspective, elevation, top view), press right click on a wall and see below the menu.

You can use the commands below:

Surface material edit: you can change the material for selected wall through the list of available materials of 1992.
Reset surface material: cancel the previous action.
Reset item material: cancel the previous action in surface of selected wall.
Delete: delete the selected wall.

Note! In case there are more than one walls in floorplan, this option will delete all of them.

Delete wall: delete the selected wall.