It's Settings > Customize Toolbars > Keys in the English version, if you want to edit hotkeys.
If you just want to restore the New Folder button to the default toolbars, e.g. after accidentally deleting it, here is the button which you can download and drag to your toolbar while in Customize mode:
- New Folder.dcf (1.9 KB)
- The Button .dcf Files section of How to use buttons and scripts from this forum explains what to do in more detail.
The default Ctrl+N hotkey is part of that button. If you don't want the button and only want the hotkey, you can make a standalone lister hotkey which runs the CreateFolder command.
You can also right-click an empty spot on the toolbar where the New Folder button used to be and use the option to reset the whole toolbar to factory defaults, if there aren't other changes on the toolbar which you want to keep. Another option next to that will reset all toolbars to defaults, if ever needed. You might want to create a backup of them first, just in case.