Guild Wars 2

Did a search, couldn’t find a list.

There are some obvious ones, but others like the More Damage to vulnerable enemies in water one are harder to tell without testing.

Does anyone know?

Basically, every damage trait works, if the conditions required by the trait is met (+20% dmg to vulnerable enemies while in water attunement for example).
But as was said above, the only trait dedicated to conjures is the Conjurer trait.

Piercing shards work.

The only trait that is tied to the conjures is Conjurer.