Welcome to programming life and good that you found out why 
Its very often even for non-newbie spent lot of time figuring why it isn’t working, so no worries
For me I only use collapse node to hide things that could never be function, and they involve too many one-time calculation and make the graph complex, like hit result data or fetching values. Copy collapsed graph requires special attention, like to update variable, ensure events aren’t duplicated, etc