How to reproduce:
1. Open the user’s attached project “UIBuilder.zip”
2. Open Window > UI Toolkit > UI Builder
3. Press the '+' icon and Create New USS or Add Existing USS in the StyleSheets section
4. Add a new selector by typing in the selector box in the StyleSheets section

Expected result: Selector’s name is visible
Actual result: Selector’s name is invisible

Reproducible with: 2021.3.17f1, 2022.2.4f1, 2023.1.0b2
Could not test with: 2020.3.44f1 (errors after downgrading)

Reproduced on: macOS M1 v10.15

Notes:

* Foldout names are not visible in the UI Builder window
* When opening the foldout, the name is visible, but its item names are not
* The selector window is displayed as empty