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In the screenshot below taken from the CRM application that comes by default in Joget's installation, the Sub Form is used in the Approval form.
Figure 1: Sub Form inside a Form
Figure 2: Sub Form Properties
ID: Element ID
Label: Sub Form Label
Form ID: Form to be referenced/loaded
Read Only: Determines if this element is editable
Display Field as Label when Read Only: Display the value of the element as plain text when element is set to be as read only.
Display without frame?: Remove default styling applied to Sub Form.
Figure 3: Sub Form Properties - Advanced
If the Form used in Sub Form stores in different table, one may configure this particular section.
Parent Field to keep Subform ID: ID of the field in the parent form to store the Sub Form table's primary key.
Subform Field to keep Parent ID:ID of the field in the Sub Form form to store the parent table's primary key.