Steps to reproduce:

1. Open a Unity Project
2. Import TextMeshPro Essential Resources via Window > TextMeshPro > Import TMP Essential Resources
3. Import TextMeshPro Examples & Extras via Window > TextMeshPro > Import TMP Examples and Extras
4. Create a Text (TMP) GameObject via GameObject > UI > Text - TextMeshPro
5. Select the new Text (TMP) Object
6. In the Text Input section on the TextMeshPro - Text component, add the below text: 

<font="Anton SDF" material="Anton SDF - Drop Shadow">Test</font>

1. A SubMesh GameObject should be automatically created as a child object of the Text (TMP) Object
2. Try to delete this SubMesh GameObject by either selecting it and clicking the delete key, or right-clicking on it and clicking delete
3. Observe that it doesn't delete. This is expected as the font is still being used in a rich text tag
4. Press ctrl + z to undo

Actual results: A duplicate of the SubMesh is created in the Hierarchy, and the warning 'Child GameObject 'TMP SubMeshUI [Anton SDF - Drop Shadow]' was not registered into undo system and became dangling during an undo operation.' is logged to the console

!image-2024-12-05-12-30-09-711.png|width=975,height=41!

Expected results: A duplicate of the SubMesh is not created, and there is no warning logged to console.

Reproducible with versions: 7000.0.0a11, 6000.1.0a8, 6000.0.30f1, 2022.3.54f1, 2021.3.45f1

Not reproducible with versions: - 

Can't test with versions: 

Tested on (OS): Windows 11

Notes: 

• In 2021.3 there is no warning when undoing, but the SubMesh still doubles up. In all later versions the warning occurs