No Fall Damage Source Commands

Activate Once: /scoreboard objectives add Falling stat.timeSinceDeath
This command adds the timer objective.

Repeating: /scoreboard players tag @a add NotFalling {FallDistance:0.0f}
This commands gives players a tag if they are not falling.

Chain: /scoreboard players set @a[tag=NotFalling] Falling 0
This command resets the timer score if they are not falling anymore.

Chain: /effect @a[tag=NotFalling] jump_boost 0
This command removes the jump boost effect if the player is not falling anymore.

Chain: /effect @a[score_Falling_min=9] jump_boost 1 255 true
This command gives players jump boost if they have been falling for at least 8 ticks.

Chain: /scoreboard players tag @a remove NotFalling
This command removes the tag.