Directly copying from the OOo Trinity Forum:

As anybody maybe knows, a lot of physical, mathematical, algebrical and other
abstract stuff are linked to strange words and signs ( expecially mutuated from
greek language and so on). To get them all any user shall go to Insert > Special
Character... or simply using the combo shift+command+O , right?
E.g. if you need to write 4-5 different types of characters, every time for any
formula (or even just the text itself), switching from one to another, you get
simply mad and bored!

In my opinion it would be great if a new simple feature were added in the Oo's
WRITER in order to make our texts easer to be filled up Wink
A small table in which every obj (special characters in particular) used with a
high frequency is entered via drag+drop or even simplier just clicking the
preferred item once.
So every time I need a different character I'd just choose/click it ('cause
maybe previously intered, or, if not yet, I'd enter it for the first time) from
the table, instead of searching it by the same old boring switching action.