I am triyng to shoot an arrow with a custom NBt tag, so i can detect it later, how can i do it?

There is a block within MCreator under the "Projectile" tab that allows you to shoot all the base-game projectiles like arrows, fireballs, wither heads, etc.

You just have to add entity NBT data to the flying arrow. You can use the "immediate source entity" block to target projectiles.