Add the header fields of Sales Order in Form Settings

Hi,

I want to make certain header fields in Sales Order as invisible, which I am able to do using SDK. However, I want to give the choice to the user whether to see or hide those fields, so I want to add the header fields in the Form Settings window of the Sales Order form. Lets say I want to hide the Contact Person field and provide the setting for this field in the Form Settings for Sales Order.

The Form No. for the Form Settings window is 998, but it is the same for Form Settings for any other window, like Production Order, Bill of Materials,. etc.

How can I track that the Form Settings window has been opened for Sales Order, and only then add the field "Contact Person" in the Form Settings window?

Thanks.