macos - Keyboard shortcut to unhide or unminimize a window in OS X - Super User

To restore one of many minimized windows (cmd-m) using only the keyboard:

Start with a minimized window
Cmd + tab to the application icon (Continue to hold Cmd).
Tip: After pressing Cmd + tab once, you can also use arrow left (and right) when holding the Cmd key, to quickly go to the application. This is a handy combination with the next step.
While holding Cmd, push the up (or down) arrow key on the keyboard. This will bring up a list of all the application's windows (You can release key command key once the window list view comes up if you like)
Push the down arrow key to select the minimized windows.
Use the left and right arrow keys to select the minimized window you want
Push enter to restore the window and bring it into focus (make it the selected window)
(Tested on OSX Mountain Lion. Step 2b tested on MacOS Sierra)...

Read more here: macos - Keyboard shortcut to unhide or unminimize a window in OS X - Super User.