Can detached screens by "imported" inti active session?

I have a few screen sessions that I started from the native shell. Now, in order to switch from one to another, I always detach the current and re-attach the one I want to switch to which works fine but it would be great if my active screens could be "imported" to an attached session so that I can simply switch between screens with ^a n & ^a p. Is there an option to do this? **EDIT1**
I realize that I can multiple sessions within one screen but what I'm wondering is, if I can import existing sessions?