sorry for late answer, didn't see your post
so what will you need to do is, on Player Shoot Bow Event:
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You make the player ride the projectile using:
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The UUID of the entity will be a Game Value
You can grab one from the Values iron ingot (should be a Nametag), right click it, go to Informational Values (Nametag), and select UUID (ENCHANTED Nametag), then shift-right click with the Game Value while looking at air and change its Target to Projectile, this will make it so the game value returns the Arrow's UUID, you can then put the game value in the Ride Entity chest and you should be good to go