Can apps on an external display be moved to a new space on disconnect?
Looks like if you create a blank space on your laptop side of things and place it in the Desktop 1 spot all the external display apps will go there on disconnect. Only weird thing is when you reset your computer if you aren't plugged into an external monitor then some of the apps seem to move around a little bit, otherwise this method seems to be exactly what I was looking for.

Cheers