How to reproduce:
1. Open any Project
2. Navigate to Project Settings > Scene Template
3. Scroll down and press "Add Type..."
4. Using horizontal mouse controls scroll right (Mousepad or horizontal scroll on a mouse)
Actual result: The dropdown menu can be scrolled horizontally but the horizontal scroll bar is not present
Expected result: The dropdown menu has a horizontal scroll bar
Reproducible with: 2021.3.34f1, 2022.3.17f1, 2023.1.20f1, 2023.2.7f1, 2023.3.0b4
Reproduced on: macOS 14.2.1