Answer
Rather than embedding the special character directly in the PL/SQL source, express it using UNISTR() with its Unicode hex code point — for example UNISTR('LEVERANT\00D6RSFAKTURA') for the Swedish word containing 'Ö'. You can find the hex code for any specific character with ASCIISTR('Ö') FROM dual. Dev Studio's own parser is stricter about literal non-ASCII characters in source files than PL/SQL Developer or the core deployment tooling, so encoding them via UNISTR sidesteps the parser's character-set check entirely.