
They look correct in Delphi IDE translation editor but replaced with "?" or converted into ANSI characters without diacritic symbols.

As a result the file is in unusable in SIL editor

SIB file export option will be available if you select top-node in the left-side tree (Translations) but this will save all the translations properties into the file, because SIB can't contain only separated properties.
StoreAsUTF8 is a property of TsiLang component and it was introduced quite long time ago.>Set StoreAsUTF8 property to True
Same question.
Where this option in Translation Editor is?