How to pass variables from ABAP program to workflow?

Question

I am creating a container for the function to pass some variables to the workflow. Below is the code of how I am creating the container and adding elements and tables to it.

swc_container lt_input_container.
    swc_create_container lt_input_container.
*Set container element
    swc_set_element lt_input_container 'HeaderData' wa_header.
    swc_set_element lt_input_container 'HeaderDataAdd' wa_header_add.
    swc_set_element lt_input_container 'Language' sy-langu.
    swc_set_element lt_input_container 'Testrun' v_testrun.
*Set Container table
    swc_set_table lt_input_container 'ItemData' it_item.
    swc_set_table lt_input_container 'SenderItemData' it_sender.
    swc_set_table lt_input_container 'PeriodData' it_period.
    swc_set_table lt_input_container 'SenderPeriodData' it_period_send.

    MESSAGE 'Sent for approval. Check mail for further updates.' TYPE 'I'.
*Trigger Workflow
    CALL FUNCTION 'EWW_WORKFLOW_START'
      EXPORTING
        x_task          = 'WS99600001'
      IMPORTING
        y_workflow_id   = lv_workitem_id
      TABLES
        x_container     = lt_input_container
      EXCEPTIONS
        invalid_task    = 1
        no_active_plvar = 2
        start_failed    = 3
        general_error   = 4
        OTHERS          = 5. 

Next in the approval of the workflow, I am trying to get the container as shown in the below code:

swc_get_element ac_container 'LEVEL' l_wflevel.  
swc_get_table ac_container 'PeriodData' perioddata.

The interesting thing is that in the ac_container (while debugging) I do not see other tables and elements (like SenderItemData). I see only level and perioddata in the debugging.

Can someone please help me figure out how to get all of the container elements and tables in the workflow?