As you probably know, I’m a big fan of Charles Choi’s Casual Suite. His latest offering deals with registers, rectangles, and windows. Much as I like the Casual Suite, I won’t be using these latest menus. Choi, as usual, is absolutely correct about the various bindings being difficult to remember but I can remember that Ctrl+x r is the prefix for both registers and rectangles. If I type Ctrl+x r and wait a second, which-key will pop up a display with all the completions. This seems easier to me than invoking a Casual menu.
As for windows, I hardly ever want to rearrange them. Mostly I just want to switch focus between them and for that the excellent ace-window does the job nicely and I have it bound to Ctrl+x o one of the first bindings you learn as Emacs beginner. The only rearrangement I ever want to do is to switch two windows and ace-window does that if called with the universal argument.
Of course, all that’s just me. You may not use which-key and may often move your windows around. If so, Choi’s solution may be just what you need. He even has bindings for using the numeric keypad keys if you have a full size keyboard. If you already have Casual installed, all this is already available and all you have to do is specify some bindings for it as shown in Choi’s post.