Reproduction steps:
1. Create a new project
2. Create a Standard Element (e.g. GameObject > UI Toolkit > Standard Elements > Button) and save UXML file
3. Select newly created Standard Element in the Hierarchy
4. Double-click on the Inspector tab to maximize it
5. Observe the Inspector
Actual result: The Inspector becomes blank
Expected result: The Element's parameters remain displayed in the maximized Inspector
Reproducible with: 6000.6.0b8
Not reproducible with: 6000.7.0a4
Couldn’t reproduce with: 6000.0.81f1, 6000.3.22f1, 6000.5.8f1, 6000.6.0a6 (No Standard Elements option)
Reproduced on: Ubuntu 24.04, macOS Tahoe 26.5 (M4)