For this, you only need a 2 entities. A triggermultiple(brush), and a filterdamage_type(entity).
make a filterdamagetype and name it "dmg" (no quotations) Also set the filter to "disallow" now in the select for the damage typ "fall"
now make the entity triggermultiple, select the texture application tool > type in trigger > select the block tool > make the trigger brush in your map where you wan't people to be rewarded with no fall damage > tie the trigger brush to the entity "triggermultiple"
My Output Named: OnTrigger
Targets Entities Named: !activator
Via This Input: SetDamageFilter With A Parameter Override of: dmg After a delay of seconds: 0
Ontrigger is in the dropdown menu > means "when triggered" you got to TYPE in "!activator" wich will activate the trigger you need to TYPE in SetDamageFilter aswell wich will "turn on" your filterdamagetype "dmg" is in the dropdown menu aswell.
now anyone who touches the trigger_multiple will be immune to fall damage