In Ubuntu Fn+F2 is used as shortcut to rename a file. But this is not working for me. Probably I changed some keymap or configuration somewhere. How can I make this work again? How can I set Fn+F2 as file rename shortcut?
I think it's possible that you're just misremembering the correct shortcut.
To rename a file in Nautilus, simply select the file and press F2 (without pressing the Fn key).