Double Jumping Concept (Commands)

Scoreboards:
1: /scoreboard objectives add JumpDetect stat.jump
2: /scoreboard objectives add JumpDelete dummy

Commands:
1: /effect @a jump_boost 1 4 true
2: /execute @a[score_JumpDetect_min=1] ~ ~ ~ summon Shulker ~ ~-2 ~ {CustomName:"JumpPlatform",NoAI:1,NoGravity:1,CustomNameVisible:0,ActiveEffects:[{Id:14,Amplifier:0,Duration:20000000,ShowParticles:0b}]}
3: /scoreboard players set @a[score_JumpDetect_min=1] JumpDetect 0
4: /scoreboard players add @e[name=JumpPlatform] JumpDelete 1
5: /tp @e[type=Shulker,score_JumpDelete_min=12] ~ ~-500 ~
6: /execute @a ~ ~ ~ /teleport @e[name=JumpPlatform,c=1,r=3] ~ ~-0.7 ~