The application generally supports Unicode, which means non-ASCII characters are allowed in track names, as well as part and preset names. All valid UTF-16 code points are allowed. Note however that in exported MIDI files, non-ASCII characters will be replaced by question marks, because the MIDI file format only supports ASCII track names. This limitation also applies to the Export Song command, because it uses the MIDI export internally.
ASCII here means printable ASCII, excluding control characters, in other words the 7-bit characters ranging from 32 to 126 decimal; characters outside this range are considered non-ASCII.
The Graph bar optionally supports Unicode, but the option is disabled by default because it increases overhead. To enable it, set the Graph Handles Unicode option to true.