You can use Custom Ceiling to design lighting effects for walls, floors, and ceilings. Follow the steps below to add lighting lines by area:

Adding Lighting Lines by Area:

1. Enter Custom Ceiling mode. First, draw the area where you want to design the lighting lines and adjust the thickness of the area relative to the ceiling/wall to create a stepped structure.

2. Click on the designed area, and then click Edit part in the parameter panel on the right.

3. In the left panel, go to Material library – Slideline – Corner line – Decorative line, and search for "white glowing line" (ID: 168944896) to add the material.
   Note: The brightness and color of this lighting line cannot be adjusted.

Method for One-Sided Lighting Line:

1. Use the Polyline tool on the ceiling or wall to draw a one-sided line. Click on that line, then select 'Fill tool' from the toolbar.

2. In the left panel, go to Sideline – Corner line & Decorative line & Baseboard – Decorative line, and search for "white glowing line" (ID: 168944896) to add the material.
   Note: The brightness and color of this lighting line cannot be adjusted.

3. Alternatively, you can search for "luminous keel" in the Electrical Appliance or Sideline section. Use the T key to rotate, resize, and move it.