I'm not necessarily averse to trying an online editor
All that I have seen are hosted editors. In other words, you can edit the files that are maintained on that host with the supplied editor. If you copy your html pages and put them on another site, you would not be able to use that original editor to modify the site. Nasty limitation. If service goes down, prices go up, or other problems happen, you have no recourse. No way to move the site.
I have never seen online editor that will allow you to open your own chosen site files from ANY host.
Ex: hosted editor on xzy.com that allows you to load in/edit pages hosted on different company's server like
my favorite host totalchoicehosting.com. A service like that might be interesting but I don't know that it exists.
You can use editors built into browsers if you don't mind HTML editing...but that moves you away from the CSB type building.