How to add approval field in form page
After you set up approval flow in design mode, you will find that it is shown as a field only on the listing page field picker but not on the form page.
If you want the approval flow to be shown as a field on the form page, you may configure it by following the steps below:
1.Add a selection field in the design mode without adding any selection, then save the design.
2.Double click the field ID below the field name to change the field ID.
3.Enter "312", click "OK" and save.
As shown below, the approval field now appears on the form page.