As of this morning I added a Drafts functionality to the Collective Forum as it seems to be something that will be of use to Role Players among others.
You'll notice a third button on writing a post which reads "Save as Draft" which is to the right of the Preview and Post buttons.
Clicking that button will save whatever you are working on to a Drafts folder for you.
You can access your drafts through the Profile link in the Collective Menu Bar.
The drafts will also appear when you attempt to post in a thread you have made a Draft in as well.
If there are any questions or problems, please let me know...
Tera
Collective Admin