Take a look at the Tools menu - and the documentation of External Tools (also called Custom Tools, but not indexed as such). You can set up your favorite editor there. I think Notepad is set up as the default - since it is present on all versions of Windows that EA has run on.
As I said, you can assign another editor, whether in place of or as well as the EA default. You can also set up arguments that can be passed at the time you open the tool - it is possible to set up the same tool several times, each with different arguments, or none. These arguments can be translated by EA to insert run-time values. Once again, see the EA documentation.
You don't seem to be able to set up a keyboard shortcut, at least not a 'hot key' combination. You can set up keys for quick menu navigation though.
For example, I set Notepad++ to be my default external editor. Once I do this I can quickly open the application. Note that I also use the same tool for viewing some code files (such as XML and DDL) but specifically excluding others (such as Visual Studio languages, which I want VS to handle). These additional 'tool' settings are done elsewhere in EA.
Once you've done this - it takes much less time than reading my post - you can quickly open an editor. The cut and paste still remains for you, but at least you are part way to what you need.
David