I am 95% sure that you can’t use the xdot attributes to fully drive Graphviz output. (see below about the other 5%)
However, you can make many changes using the dot language, either stand-alone (no layout engine) or using pre- or post-processing. - see the FAQ (FAQ | Graphviz).
Here are some examples:
- A radial Graphviz engine (pre-processor)
- Fun with Edge Labels!
- Stupid Dot tricks
- Ortho edges and ports - a partial work-around
p.s. The 5% - it seems that you can make some changes to the Root graph via the draw attribute, but not to any other objects (maybe). Huh!