There is no in application method to do this.
If you are on Linux you should find librecad.conf in your home folder:
~/.config/LibreCAD/LibreCAD.conf
On Mac there should be a LibreCAD.conf too, but I don't know the exact path.
On Windows systems the preferences are stored in the registry:
HKEY_CURRENT_USER\Software\LibreCAD
It is possible to export/import these settings with regedit.
For both it is important to know, that there are also path information stored in preferences. Thus this may break LibreCAD on the target system. Backup the old files!
Both, the Linux/Mac conf file and the Windows registry export are text files which can be adjusted with a simple text editor.
But, do this at your own risk, you should know what you do if you do it
Armin
investing less than half an hour into Search function can save hours or days of waiting for a solution