Yes, at least in the IDE, where the Ask and Answer stacks are each in their own stackfile.
You know the message path well; after a message reaches the stack it goes to the engine...
... unless you have a script acting globally, such as a library or a backscript.
The stacksInUse refers to those stacks that have been brought into use as libraries. Anything listed there is global in scope, such as a library with a mouseDown handler.