flash (macromedia): I'm not really sure how to properly describe this so please bear with me.

Say you create an animated action on your main timeline with a symbol. Then
you decide you want to take that action and put it into a movie clip so that it
migrates across the screen. Since it is already on your main timeline, how do
you take that layer, and convert it into a movie clip?

I hope I've described this clearly enough.

Select all the frames on the layer, right-click on them and select copy
frames. Create a new symbol. Right-click on the first frame of this new
movieclip and select paste frames. Go back to the main timeline and delete the
layer.