I know that Ctrl + N is to find classes and it is very useful. But what about methods?
Intellij IDEA 2017.3.4 - 2018.2 (Ultimate) on OSX
CMD + fn + F12
will show all members of the current class in a popup window, then you can search method in that class.
BUT, this answer is depends on your Keyboard setting. If your keyboard setting in
System Preferences > Keyboard > Use all F1, F2, etc. keys as standard function keys
is selected, then the shortcut becomes
CMD + F12