Folks,
I have been following this discussion perhaps it is time for my story.
I teach Hebrew and Greek in a Chinese language school and must prepare material for students in those languages. I use Openoffice and now Libreoffice exclusively. I used to insert the needed characters special characters.
It wasn't enough to have the fonts. I wanted to work within OO and LO and needed a way to key these into my documents directly.
I finally found some really decent fonts (SIL) and a splendid keyboarding program from Tavultesoft www.tavultesoft.com and . Now I can type these languages nearly as easily as English ... accents ... jots ... tittles ... breathing marks ... everything. Some folks in a Greek monastery provided a Tavultesoft keyboard that runs inside OO and LO.
Tavultesoft is proprietary, but it has answered my problems (Even Chinese!). Maybe it will do for you as well.
This link goes to a list of "Best Free" keyboards. Tavultesoft seems to be a paid product.
http://www.techsupportalert.com/best-free-onscreen-keyboard-osk.htm#Click-N-Type
I used MS's version for a computer that required a USB mouse and keyboard since it did not have PS/2 plugins. I did not have a USB keyboard, so I had to use the on-screen one till I got a USB adapter for the keyboard I had. Now I use a remote desktop viewer program to use that number-crunching computer so I do not need desk space for it.
So these on-screen keyboards do work. I have an old tablet PC that defaults to a mixed English and Japanese keyboard layout, for whatever reason, but they do work when you need to use a different keyboard layout than English.