By request, here's a userstyle (which the site can auto-convert into a userscript if needed) for hiding the chapter progress indicator that sticks to the top of the viewport:

FiMFiction.net - Hide chapter scrubber bar

(I actually like it but to each their own)

2335853 What chapter progress indicator?

2335856

I've added a screenshot.

2335903 I have not seen that before today. It must be new

2336076

Less than 6 hours old, if my sense of time isn't horrendously broken.

2336142 Ultra gay