yes it's possible, you have to use the picture in picture tool.

I think its only in the plus version though, if you have the standard studio package then i'm not sure, although there is probably a workaround.

as you only have two video track in studio ( thats if you have the plus version), if you want to do more than two video's then you have to do the first two. render it out as an avi then do a new project with the avi file and add the next video and render again and so on.

here's a link to a tutorial that does this with photo's but the basic process is the same for video.
http://www.goldenpenpublications.com/