Add custom repositories is still there, it was moved to an overflow icon (3 dots) in the top right corner where the refresh icon was before. But there’s currently an issue where no icons are appearing in Supervisor 221. You can still access it if you know where to click, the icons are just invisible at the moment.
I think the issue is because Bram is changing the way icons are handled in 0.110 and this incorporated something from the upcoming beta…