(Test results for version 4.0c Beta 1)
If I do a Basic Search, and type in "g:logos", I can select the correct greek word from the dropdown list. In which case, the search field changes to "greek:λόγος ", which is correct, and works as expected.
HOWEVER, for Latin as follows, it fails.
In Basic Search, type "l:ipso" and select the first from the list, the seach field changes to "l:latin:ipso", which then fails to find anything.
Manually changing the prompt to "latin:ipso" does indeed find content from my library.
(Using "latin:ipso" and selecting the first dropdown item, searches "latin:latin:ipso" which does in fact work correctly, but is clearly not right having a double label)