• Add Item to the scene
• Add Rectangle to the scene as the child of the previous Item
• Right click on Item in navigator and choose "Create Component"
• Click OK
• Right click on Item in navigator and choose "Edit Component"
• Click the @ sign next to Rectangle on navigator to expose it as alias
• Save the project
• Go back to main file
• Select the Item in navigator
• Search for any of the exposed properties from the subrectangle (E.g. "Border" or "Color")

-> The exposed properties are not included in the search