The editor needs a field for the gabc header

[ghost]

Background:
In https://gregobase.selapa.net/chant.php?id=15174 there are the neumes. When I tried to run the file, it complained that the nabc-lines parameter in the header is missing. I added it and it kept crashing, by try-n-error I figured out, that the correct line in the header is
nabc-lines: 1;

Now I wanted to upload the fix, but I couldn't as the header is auto-generated. I don't see any possibility to download and upload raw files either. Somehow, I need a textbox in the editor to edit additional header values, additionally to the standard, auto-generated parameters there.

Problem:
The issue is in /chant_edit.php at around line 258.
I don't know php-programming yet, though some html and other languages.

I couldn't figure out, what $c does there and therefore couldn't fix the problem. With comments I might have been able to. So I can only complain. Sorry.