I just installed LibreOffice 3.4.3. On the launch screen I see that there is an option to "Open..." and there is a drop down menu with the most recently opened documents.
Please, how do I clear this list?
you could try http://extensions.services.openoffice.org/project/histmngr but I don't know if it will work with LibreOffice.
If this does not work, you could try and edit the file registrymodifications.xcu - I would be very careful of doing this though.
The latest version of BleachBit is also worth a look at as this may well clear the recent file list for you (it will be under openoffice.org not LibreOffice) - does not work in my system but should do apparently.
Linux Mint 15 LibreOffice 126.96.36.199 : OpenSUSE 12.3 LibreOffice 4.0.3
History Manager extension is out of
date, but there is a new extension that might work for you.
History Master 1.1.1 from OpenOffice extensions