Steps to reproduce:

1. Navigate to Data collection -> Templates (or Hosts),
2. Open any Item or Item prototype that has preprocessing steps,
3. Go to the Preprocessing tab,
4. Click the Test button (or Test all steps),
5. In the opened "Test item" modal, observe the Value field and its preview,
6. Start typing or editing the text in the Value and/or Previous value field.

Result: The preview disappears from the modal form. See video:

Expected: The value preview should remain visible or update dynamically to reflect the changes, providing consistent feedback to the user while they are editing the test data.