Apple - How can I re-enable the (display) sleep shortcut on macOS Sierra?

Things definitely have changed:

⌥⌘⏏ (Cmd-Option-Eject) to put your machine to sleep no longer works in Sierra.

Supposedly, ⌃⏏ (Ctrl-Eject) has taken its place, but it doesn't work on my late-2012 iMac.

At least according to the documentation, that is the only change - compare below.

Sadly, you cannot bring the old shortcut back (at all?), because defining keyboard shortcuts in System Preferences > Keyboard > Shortcuts > App Shortcuts doesn't allow you define shortcuts involving ⏏ (Eject), and, in fact, even shortcuts that are permissible do not seem to put the machine to sleep (flickers briefly, but stays awake).

Sleep-related shortcuts as of macOS Sierra:

Source: https://support.apple.com/en-us/HT201236

Sleep-related shortcuts as of OS X El Capitan:

Source (link effectively dead, redirects to the Sierra page): http://support.apple.com/kb/ht1343

To the best of my knowledge there are only three macOS keyboard shortcuts that have any sort of sleep functionality. These are as follows:

• Power button - Hold for 1.5 seconds while your Mac is awake to display a dialog asking if you want to restart, sleep, or shut down.
• ControlShiftEject - Puts your display to sleep.
• ControlShiftPower button - As above, this puts your display to sleep.

It seems to me that the second keyboard shortcut is the one closest to what you're describing - instead of CommandOptionEject it's ControlShiftEject.

Is this what you're after? Or had you in fact been using CommandOptionEject previously?

You can also check out the Mac keyboard shortcuts page for a more detailed description of macOS keyboard shortcuts.

If you're looking for the same dialogue window that holding the power button used to preset, you can access it by using the fn+Power combination. No need to hold anything down. I'm not sure if this is a change in macOS Sierra, but I just found the combination this morning by accident. Hope it helps!