kylania, the notation comes from the GNU Emacs
notation for keyboard shortcuts. As in Emacs, modifier keys like Control, Alt (or Meta), Win cannot stand alone in DCS, and you cannot press two ordinary keys at once either. DCS, unlike Emacs, distinguishes left and right modifier keys, so a little r indicates the right modifier.
All of the modifiers are listed in the very first table for clarity.
"W-C-R" for instance means press Windows and Control modifiers and the R key.
Consecutive presses of W, C and R keys would be denoted "W C R".
The Emacs notation is very concise and precise at the same time, and I like that very much about it.
If I get around to it, I might check how the table looks with your longer notation. But as you can see, the second column is already used almost completely by some of the more complicated commands. So it would probably mess up the compact presentation.
Anyway, there are already other keyboard references around with your proposed style and A-10C even has a spreadsheet with all keyboard commands in the Doc folder.