Frequently asked questions - Writer
How do I insert a non-breaking hyphen when the process indicated in the help doesn’t seem to work?
The Help indicates that you obtain a non-breaking hyphen by the Ctrl+⇧ Shift+- key combination, the - being the one from the numeric keypad.
On some systems, it appears that this key combination does not work directly. To work around this issue, the numeric keypad has to be deactivated.
Another solution consists of selecting from the▸ ▸ menu.