If you were desperately looking for a Rebol Editor which supports Rebol Syntax Highlighting (see an old discussion here) and even Code Folding, I just stumbled upon Programmer’s Notepad (an opensource project in Visual C++):

You may not like the color scheme chosen for Rebol but you should be able to easily customize it by editing its XML source.
Until now I was using Notepad2 (though it didn’t support Rebol syntax, it could nicely delimit the Rebol brackets which was really a great feature) but PN seems a good replacement. Notably Programmer’s Notepad supports a Great Project Management Interface (I love the “Magic Folder” feature) - much more complete and easy to use than Crimson Editor (which has also Rebol Syntax HighLighter).

To install Programmer’s Notepad for Rebol, first choose a package to download from the page here. Install it and then download Rebol Scheme into the schemes subdirectory of your install directory.
Then don’t forget to associate .r file with rebol scheme in Tools -> Options -> Files/add to do so:

If you have further questions visit its forum.
















Thanks for the nice comments and write-up!
What’s the trick to get PN to execute a file with rebol.exe?