Today, I got a business requirement to remove the Effective from and Effective to fields from the header of the quote.
First, I thought that would be very simple to do and opened the Quote form. And noticed that those fields are Locked fields.
The work around is very simple.
Add the locked fields on the form. In this case, Effective from and Effective to.
Open the Properties of the field and uncheck Visible by default.
Select the Header on the ribbon and now you will be able to remove the locked fields from the header. You can add the fields as per your requirement.
Hope this helps.