Steps to reproduce:

1. Create a new Unity project using the Universal 3D template
2. Create a new Terrain (GameObject > 3D Object > Terrain)
3. Click the "Paint Terrain" button in the Inspector window under the Terrain component
4. Click the "Edit Terrain Layers..." button
5. Select "Create Layer..."
6. Select any Texture 2D (reproduction used "URP")
7. Click on the newly created layer "NewLayer 1"
8. Repeat step 4
9. Select "Remove layer"
10. Observe the Inspector window

Actual results: "New Layer 1" Terrain Layer settings remain in the Inspector window

Expected results: "New Layer 1" Terrain Layer settings are no longer in the Inspector window

Reproducible with versions: 2021.3.51f1, 2022.3.62f1, 6000.0.50f1, 6000.1.4f1, 6000.2.0b3

Tested on (OS): macOS Silicon Sequoia 15.3

Notes:

• The Terrain Layer settings remain until create or add layer button is pressed or a new layer is selected
• Closing and reopening still shows the removed layer material settings