Create a list of records with lists

Hi,
i have a coumple of records/objects which have also lists.
image
I need to create a new SIMPLE LIST out of this.
By doing so
PLUCK(pageVars.sessionslist,“lessonslist”)

i just get this (values are just examples)
image

So its a list of objects instead a simple list.
Only way i could find is with some flow logic, but this seems not very smart. I hope its possible just to get to the same solution with some formula.