Obscure Windows 7 question

[alitalf]

Does anyone know how to add items to the contextual NEW menu that you see on right click? At present, it does not give me the opportunity to create a new ODT or ODS file dirctly in a folder, though some sorts of files can be created, for example txt. I have tried following the instructions at http://www.askvg.com/how-to-add-remove-items-from-new-menu-in-windows/, but that did not work. Then I looked at how .rtf is handled, and added a second item to the ShellNew key. The extra value is ItemName, something that all other filetypes that can be directly created in folders seem to have. The value for that in .rtf is: @%ProgramFiles%\Windows NT\Accessories\WORDPAD.EXE,-213 but I do not know what is the environment vvariable needed for Libre Office, so I used: C:\Program Files (x86)\LibreOffice 3\program\swriter.exe in the vain hope that it would be workable. I have no idea what to do to determine what number, if any should be appended. Unsurprisingly it doesn't work. It was a very slim chance. Maybe an error message would have given a clue, but there wasn't one. Any ideas anyone?