a simpler way is only to use one speech bubble - but then they have to say the same
You can do it for example so that you will create an extra character whose display name will be
MELL AND JOE
Or you will make NARRATOR
NARR
Joe: This is insane! [nl] Mell: this is great!
but there is no way how to make 2 separate speaqchbubles without overlays