I've spoken with some users that do debugging in multiple sessions, and several of them have pointed out that what they would really like to be able to 
do is have multiple sessions open simultaneously so they can look at both at once.

One possible way of dealing with this would be to allow  the user to choose a "Show session in new window" item from the contextual menu of a 
session and this would then display a copy of the debugging window focused on that session.  There are other approaches that might be considered, of 
course.

This is certainly an "advanced" feature, in that the casual user (who does only single session debugging) won't care.