*Steps to reproduce:*
# Create a new URP project.
# Assets > Create > UI Toolkit > UI Document and open it in UI Builder.
# From the Library, add a ToggleButtonGroup to the hierarchy.
# From the Library add three Buttons as children of the ToggleButtonGroup.

*Either:* 
* Save

*Or:*
* Undo and redo.

*Actual results:* All child buttons exit the ToggleButtonGroup, and remain outside.

*Expected results:* Buttons should remain children of the ToggleButtonGroup.

*Reproducible with versions:* 6000.1.0a4, 6000.0.28f1, 6000.0.20f1

*Not reproducible with versions:* 6000.0.19f1

*Can’t test with versions:* 2022.3.52f1, could not find ToggleButtonGroup

*Tested on (OS):* Ubuntu 24.04