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After Items and Families have a linked relationship and nested families are linked to items, the process of created sub items based on the nested families can be automated.
Open the Items to Families window
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Select the main family that includes nested families
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Select Sync
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4. Check the box next to Synchronize nested families to subs this . This will build the sub item relationship based on the nested families and quantity of nested families in that family type.
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5. Select “Ok”