Use Case: 

We have an AP Invoicing forms process that currently allows the upload of a single invoice with a table for GL Coding that allows multiple entries for GL Accounts, Subledger numbers, and dollar amounts in order to split the total invoice into multiple accounts.

The users are requesting the ability to upload multiple invoices to one form, which will require a Collection.  They still need to be able to split each invoice amongst multiple GL Accounts, so that would require a table within the collection so we can have multiple records for GL Account, Subledger, and Amount.  

If not a table, then possibly the other fields such as Single Line, Number, and Currency could have a multi-value option?