How to itemize and distribute an Expense line via REST API

Summary:

I have to itemize an existing expense line (split it into personal and business expenses). In addition, I would like to provide a CCID for the business expense itemizations. 

When I create the itemization, I can see the lines appear in the GUI, as well as the table EXM_EXPENSES (ITEMIZATION_PARENT_EXPENSE_ID col correctly reflects the expense line that was itemized.

All the REST API point to the expense line (but not to the itemization). In the GUI, however, you can clearly provide the CCID for the itemized amount. 

So if an expense line for $100 was itemized as $20 (personal), $50 & $30 (business expense), then I would like to assign 2 different CCIDs for the $50 & $30 (itemized) lines.