Hi, right now the options for exporting to OmniGraffle are Work Breakdown Structure, Activity-on-Node Network Diagram, and Activity-on-Arrow Network Diagram. The former two have two options - Basic or Tables.
However, I think you're asking for an export of the graphical Gantt bars and connection lines themselves. We don't currently have such an export. What type of changes did you want to make to the Gantt chart? You might try working with the Project:Styles and Project:Colors inspectors for now.
If you would like to request this as a feature, be sure to send an email to
omniplan@omnigroup.com - this is the best way to make sure we get your feedback to the right people. The more detail and ideas you have, the better!
Joel R
Software Test Pilot
The Omni Group