the subform id
the subform's elements
if no form dialog currently opened, or sub form not found, or no sub form table field in currently displayed form, or invalid parameters
 // opens the form creation dialog for layer id=3
 JMap.Form
   .openUpdateDialogForSubForm(
     4,
     [
       id: 4,
       parentId: 3,
       elementId: 3,
       parentAttributeValueByName: {
         jmap_id: 3,
         color: "red",
         type: "tree"
       },
       attributeValueByName: {
         id: 4,
         name: "bee",
         type: "nest"
       }
     ]
   )
   .then(formMetadata => console.log("Update sub form dialog opened", formMetadata))
   .catch(error => console.error(error))
JMap.Form.openUpdateDialogForSubForm
Opens the sub form creation dialog.