documentclass[ngerman]{article}
usepackage{fontspec}
usepackage{selnolig}

usepackage{luacode}
begin{luacode}
function breaklig (s)
    s = s:gsub ( 'Verzweiflung' ,
        'Ver\-zweif\discretionary{-}{}{\kern0.05em}lung' )
    return s
end
luatexbase.add_to_callback( 'process_input_buffer' ,
    breaklig , 'break ligatures in specified words' )
end{luacode}

begin{document}

Verzweiuselig{fl}ung {V}erzweiflung Verzweiflung

end{document}