Reproduction steps:
1. Open the attached “repro_IN-72094“ project
2. Open the “/Assets/SampleScene.unity“
3. Double-click the “/Assets/NewUXMLTemplate.uxml“
4. Double-click “ListView“
5. Drag the “/Assets/NewUXMLTemplate 1.uxml“ to the “Item Template“ parameter field
6. Save the .uxml document (“Ctrl + S” button combination)
7. Close the “UI Builder“ window
8. Right-click on the “/Assets/NewUXMLTemplate.uxml“ and select “Reimport“
9. Double-click the “/Assets/NewUXMLTemplate.uxml“
10. Double-click “ListView“
11. Observe the “Item Template“ parameter field
Expected result: The “Item Template“ parameter field is set to “NewUXMLTemplate 1“
Actual result: The “Item Template“ parameter field resets to “None“
Reproduced with: 2023.3.0a16, 6000.0.0b12
Not reproduced with: 2023.2.15f1, 2023.3.0a15
Couldn’t test with: 2021.3.36f1, 2022.3.22f1 (the “Item Template“ parameter field doesn’t exist in the “UI Builder“ on these versions)
Reproducible on: Windows 10 (22H2)
Not reproducible on: No other environments tested
Note: Warning “Assets/NewUXMLTemplate.uxml (2,6): Semantic - The specified URI does not exist in the current project : Assets/NewUXMLTemplate 1“ appears in the Console after reimporting the “/Assets/NewUXMLTemplate.uxml“