How to reproduce:
1. Open the attached "GradientTab" project
2. Open the "SampleScene" scene
3. In the Hierarchy, select the "GameObject" 
4. In the Inspector, navigate to the "Test Script" Component
5. Click on the "Test" field to open the Gradient Editor tab
6. Hover on the three-dot menu of the "Presets" section

Expected results: The three-dot menu button changes color
Actual results: There is no "on hover" highlight 

Reproducible with: 6000.0.38f1, 6000.1.0b5, 6000.2.0a3

Reproducible on: macOS Sequoia 15.3 (M1)
Not reproducible on: No other environment tested