As my colleague noted, RoboHelp now only supports opening projects.
But if you read between the lines a bit, what you can do is to have a tiny scratch project that you open, then simply import the HTML page you want to make edits to. Make your edits, save them, then copy the HTML page wherever you like.
Helpful and Handy Links
Brilliant. Thanks for the tip. I might have come around to that
technique eventually, after mustering up some motivation, but I
realized I should be able to tame this Dreamweaver thing a bit too.