“AssertionException” errors are thrown when reordering elements in the Sort Column Descriptions list

Steps to reproduce:

1. Create a new Unity project using the Universal 3D template
2. Open the UI Library (Right-click in the Hierarchy > UI Toolkit > Standard Elements > UI Library)
3. Double click the Multi Column List View to add it
4. Click Confirm
5. Add an Element by pressing the "+" button in the Sort Column Descriptions list in the Inspector window
6. Repeat step 5
7. Reorder the elements by clicking and dragging on the reordering indicator
8. Observe the Console window

Actual results: “AssertionException” errors are thrown

Expected results: No errors are thrown

Reproducible with versions: 6000.6.0b3, 6000.7.0a2

Can’t test with versions: 6000.0.79f1, 6000.3.19f1, 6000.5.3f1 (due to no feature)

Tested on (OS): MacOS Silicon Tahoe 26.5.1, Ubuntu 24.04