Add html elements to an obligatory section

Hi, I have been working with fidus for a while, I am changing how the sections looks on the editor (basically adding a little title with a span to the sections, so it pretty clear in what section you are working on
My template has mostly optional sections, but one obligatory field…
With the optional sections I was able to add the little span with the title pretty easily in the Partview model
But for the one obligatory section, I have not been able to do it, the section is a heading_part, I tried looking for the part where it creates the obligatory sections, but was not quite able to find it
If anyone has any clue on how this could be done I would appreciate it
Thanks in advance!