Ak Editing 0777

On my Channel "About" page, I have a Biography section, which I can not figure out how to edit.  The Description section (1 line of text) is editable by clicking the 'pencil' icon after entering 'Customize Channel' mode, but there is no 'pencil' icon visible anywhere to edit the Biography section.
I've also tried to look in YouTube Creator Studio to find an option there to edit it, and I'm fairly sure I've looked in every page and buried menu in there, but I couldn't find one.