How to reproduce:
1. Create a new Unity project and install the Cinemachine package
2. In the Hierarchy, right-click -> Cinemachine -> Cinemachine Camera
3. Select the Cinemachine Camera
4. In the Inspector, navigate to the "Add Extension" field
5. Open and close the dropdown
6. Reopen the dropdown
Expected results: The dropdown can be reopened
Actual results: The dropdown can't be reopened
Reproducible with: 3.0.0-pre.8, 3.1.3 (6000.1.0b8)
Not reproducible with: 2.10.3, 3.0.0-pre.7 (6000.1.0b8)
Reproducible on: macOS Sequoia 15.3 (M1)
Not reproducible on: Windows 11
Note: The dropdown can't be reopened unless you restart the project, which makes it complicated to work