Steps to reproduce:
1. Create new Unity project using Universal 3D Template
2. Open UI Builder window
3. In “Add new selector…” field enter selector name (e.g “Test”)
4. Press Enter and Save USS File
5. Click and drag “.test” selector over “:root” selector
6. While holding “.test” selector over “:root” press undo shortcut with a keyboard (command+z)
7. Observe the StyleSheet window after undoing
Actual results: After pressing undo while dragging the ".test" selector over ":root," the selector becomes stuck in the StyleSheets window, it cannot be moved or deleted
Expected results: Pressing undo while dragging a selector should either cancel the drag operation gracefully and return the selector to its original position, or complete the undo without leaving the selector in a stuck/uninteractable state.
Reproducible with versions: 6000.0.74f1, 6000.3.16f1, 6000.4.9f1, 6000.5.0b9, 6000.6.0a5
Tested on (OS): macOS Tahoe 26.4.1 (M1)