Hi @pword ,
Please share the items and Default values of the Dropdown and also the Patch() function to start with.
You can also check if something like below will help in your requirement or not.
ColumnName: {'@odata.type': "#Microsoft.Azure.Connectors.SharePoint.SPListExpandedUser",
Title: Lookup(OrignalDataSourceOfLookup, Title= ComboBox8.Selected.Value).Title,
ID: Lookup(OrignalDataSourceOfLookup, Title= ComboBox8.Selected.Value).ID
}
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