That is a good idea. I know there are occasions when I would like a place to "Text" a post. I used to use the sandbox, but now I can't.
All you have to do is put your HTML on a notepad file then "save as" a .htm file type instead of saving it as a .txt file. After saving it as a .htm it'll look like an internet shortcut. Just double click it and your browser will open it as it will appear when posted.
I get $60 an hour for tech support, you owe me $2.