bug#12431: [feature request] Add info on next-multiframe-window command

[Seweryn Kokot]

Hello,

Yesterday I added an external monitor to my laptop and created two
frame; one on each screen. Then I looked for a command to cycle
between windows and frames and couldn't find what I wanted in emacs or
elisp reference manuals. I tried to write my command but without
success. Searching on the internet I found that next-multiframe-window
(previous-multiframe-window) command is what I looked for. I think it
would be useful to mention this command in both emacs manuals in
paragraphs where other-window and other-frame commands are described.

Thanks in advance,
Seweryn