That is your problem, the technic launcher is super old I doubt it supports forge on modern versions. There is literally no way to 'just use the universal' that is not how any of this works anymore.
We do not support 3rd party launchers.
There is nothing in those launchers that is required for you to make a mod pack. You can make it quite easily on the vanilla launcher.
See how BowItem creates an arrow and how fireball entity make explosions when collide
To be more specific:
Create and register the entity, maybe make a model and renderer (remember to register it) for it if you dont want it to look like a normal item flying in the sky, and summon it with your item.