Starting with version 3.7 chords are recognized based on the following rule set:
- Starts with A-H followed by an optional #, b, ♯ or ♭
- Followed by an optional chord type: add, sus, m, min, maj, aug, dim, -, +, minmaj
- Followed by an optional extension 2, 4, 5, 6, 7, 9, 11 and 13 that can optionally be prepended with #, b, ♯ or ♭
- Followed by another optional extension 5, 9, 11, 13 that can optionally be prepended with #, b, ♯ or ♭
- Followed by an optional bass note after a / that can be A-H with an optional #, b, ♯ or ♭
Granted, this will allow some unusual chord notations but it will give you more freedom in writing down chords.