Ive done this before. Basically when you get 2 of one Item you want them to 'combine' and make a level higher.
u need like a condition though, something like this.
Actions:
Trigger - Turn off this trigger
If then else (Multiple functions)
If -
number of items carried of type (tidal awakening lvl1) is greater than 1
Then -
remove item of type (tidal awakening...)
remove item of type (tidal awakening...)
Create (tidal awakening level 2) and give it to (hero manipulating item)
Trigger - Turn on this trigger
Even if the unit isnt a hero, it will still work.
and turning on/off the trigger should keep it from making multiple items. It doesnt matter whether or not u have a wait.