For those of you who could be interested, I posted a pack of Keyboard Maestro actions for OmniFocus in the Keyboard Maestro forum. Here is the link to the post:
It allows you to use Keyboard Maestro to get the selected tasks, get / set the properties of a task, etc.
May I ask you to look at this post, please: following your installation instructions, neither OF nor KM seems able to detect the Macros: different in KM 9?