How can I insert and update field data of a sub-form without adding data into the main form’s mandatory fields.

How can I insert and update field data of a sub-form without adding data into the main form’s mandatory fields.

1. I have a main form that contains a sub-form. I need to update the data of the sub-form from a function, but I am unable to do so. How can I achieve this in Zoho Creator?

2. How can I insert data into a sub-form without inserting data into the mandatory fields of the main form?