Reproduction steps:
1. Open the attached “Hopeful Dumpster Fire.zip” project
2. Open the “Assets/BugReport/Document.uxml“ file in the UI builder
3. Select the MultiColumnListView element in the Hierarchy pane
4. Navigate to Attributes > Columns > Columns in the UI Builder Inspector pane
5. Assign CellView.uxml to the Cell Template field
6. Save (CTRL+S) and close the UI Builder
7. Select the Assets/BugReport folder and reimport it (Right Click > Reimport)
8. Open the “Assets/BugReport/Document.uxml“ file in the UI builder
9. Observe the Console window and UI Builder Cell Template field
Expected result: No errors are thrown and the reference is retained
Actual result: “ArgumentException: Object of type 'UnityEngine.Object' cannot be converted to type 'UnityEngine.UIElements.VisualTreeAsset'.” error is thrown and the reference is missing
Reproducible with: 6000.0.32f1, 6000.1.0a8
Couldn't test with: 2021.3.47f1 (Could not resolve compilation errors), 2022.3.55f1 (no columns attribute)
Reproducible on: Windows 11
Not reproducible on: No other environment tested