Directly related to this previous issue: Furigana options are gone
Only this time they aren't completely missing but the menu has moved and is almost unusable instead (the former isn't the problem.) The menu is very small and cannot be scrolled. What is invisible in screenshot is unusable in browser.
Firefox 54, Linux
Chrome, Windows
I first noticed this issue in rev 2017.8.4.26700 but it's also possible that some earlier version broke the options menu.
I noticed this while reading the Help Answer on Furigana (the section about customization).
As rev 2020.8.11.37378, the 'Japanese Options' link has disappeared completely, and it appears to be impossible to customize Furigana from the desktop version of the website.
The 'options' link is present (and it works) in the mobile version, but setting e.g. "don't display furigana", saving, and then switching back to the desktop version does not remove furigana in the Desktop version; the setting only affects the mobile version. So this is not a viable workaround.
