How to reproduce:
1. Create a new 2D Unity Project
2. In the Project window, create a Sprite Asset (right-click -> Create -> 2D -> Sprites)
3. Select the created Sprite Asset and click "Open Sprite Editor" in the Inspector
4. Observe the upper left panel with "Sprite Editor", "Slice" and "Trim" buttons

Expected results: The separator line between "Sprite Editor" and "Slice" is the same as between "Slice" and "Trim"
Actual results: The separator line between "Sprite Editor" and "Slice" is thicker 

Reproducible with: 6000.0.32f1, 6000.1.0a8
Not reproducible with: 2021.3.47f1, 2022.3.55f1

Reproducible on: macOS Sequoia 15.1 (M1)
Not reproducible on: No other environment tested