Definition of Event Parameters (BOR) 
You define event parameters to supplement the system event parameters. The event parameters are displayed as event container elements and you use them in binding definitions between the event container and the task or workflow container.
There are two different types of data type reference for event parameters:
ABAP Dictionary reference
Object type reference
To create event parameters for an event, position the cursor on the event ID and select Parameters.
When you create an event parameter whose data type reference can be specified by an ABAP Dictionary table field, you should always have the system propose the relevant table fields.
Answer YES to the question Create with ABAP Dictionary field proposals?
If you want to create an event parameter with an object type reference, you cannot use field proposals. Answer the question with NO.