Is just having a button with no writing too vague? So instead of "add new feed from url" it is just a little + in a square for example.

Yeah I don’t like that part. Need to shove it in a corner probably since I don’t think it’ll be used much

Could always have an «Edit» toggle on the top that exposes the buttons to edit/add/delete feeds and otherwise have it hidden to take less space

I feel like it should probably be easier to add new feeds. I think that fits into the philosophy of constant expansion within social media, you're always opening new connections and so you don't want to hide that behind another menu.

true but that button is specifically for pasting in a feed URL I would think