I have several hours of home movies that have been digitized and are in one large .AVI file. I am able to go into MM and trim the clips, rearrange them and so forth. But what I can't figure out is how do I, for example, export a movie of just birthday parties (I have those clips segregated) or just athletic events? I want to put them on YouTube as a series of shorter movies organized by topic. I cannot figure out how to selectively choose portions of a project to export. 

I can cut/paste/copy clips within a project, but I can't seem to do it between projects. 

Is this a limitation of MM or is there a workaround?