Reproduction steps:
1. Open the attached "ussvarsuib" project
2. Open “Assets/Builder.uxml”
3. In the StyleSheets, select "VisualElement"
4. In the Inspector, go to the "Background" section
5. Hover over "Color" and click on the three dot menu
6. Click on "Set variable"
7. Click and hold on a USS variable
8. Observe the results

Expected results: The USS variable inspector does not close as long as its being held
Actual results: The USS variable inspector closes almost immediately

Reproducible with: 2023.3.0a2, 2023.3.0b1
Not reproducible with: 2021.3.34f1, 2022.3.17f1, 2023.2.4f1, 2023.2.0a23

Reproducible on: Windows 11 Pro, MacOS 14.0(user's)
Not reproducible on: No other environments tested

Note: For some versions, you may need to type in “--red-100” for a USS variable to show up