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Could you please supply us the details about the issue like in which form you want subheadings to have multiple lines or name of fields that should have multiple lines?
Right now I can only suggest you to make changes on your source code according to your needs. Please note that when you start using your source code, you need to update it every time you made a change on your form.
Waiting for your response.
I worked on the issue a little bit further. You can insert the below code to get a line break in subheadings. However you need to define width property according to your needs.
Here is a demonstration:
This code applies style to all subheadings. Yo can apply styles to subheadings individually. In this case you need to inspect elements from form source code and you need to define css accordingly.
The code for styling single element:
I hope this helps.