We can add Script Components to our AssemblyLine in addition to Connectors by right-clicking Insert Components... > Scripts > Script on the appropriate Component or section in the AssemblyLine Components window in the AssemblyLine Editor. The Script Component is started once for each entry processed by the AssemblyLine, and can be placed anywhere in the AssemblyLine.
Iterators are still processed first, even if you place your Script Component before them in the AssemblyLine.
For more information, see Script Components.
Parent topic: Scripting in an AssemblyLine