According to the feature request #2665818, the item page only shows the related items whose relation ships are not "partOf".
Then when user created a sub item, the sub item will be invisible on the item page, since the sub item is "partOf" the item.
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According to the feature request #2665818, the item page only shows the related items whose relation ships are not "partOf".
Then when user created a sub item, the sub item will be invisible on the item page, since the sub item is "partOf" the item.