subtitles coding

in my language (Slovak) have we many special characters
Subtitle autors uses more different coding tables (Unicoode or Windows 1250, ISO-8859-2, Latin2)

Q: is any possibility to change this coding on display (bazed on server or client)???

No. Plex needs UTF-8. UTF-8 works on every Plex Client.

You either send your subtitle files through a converter before adding them to Plex (under Windows there are notepad++ and Subtitle Edit)
or
you try if this 3rd party plugin may be of use to you SRT2UTF-8. Read its documentation and installation instructions carefully.