On my Symbolics VLM installation (on a MacBook Pro) I can run things in one Listener, let it running its code and switch to the next listener. I can also use the GUI to create a new Listener. I can switch back to the busy Listener and force it into a break by control-suspend. I can also reshape a busy Listener window.

Something like the LispWorks IDE, with its editor-based listener tool, does the same.