Links to instructions on how to initiate a transfer are listed within the Cost Transfer Tool - Training Materials KB article. 

Partial Transfers

After initiating a transfer, certain icons become available in the far right column, including a plus sign that allows for adding additional "To" lines: 

The plus sign can be seen in this example salary transfer:

By adding additional "To" lines, a user is able to transfer a portion of the original expense to a new funding string while effectively transferring the remainder back to the original funding string.

For example, a partial transfer of a $100 expense that effectively keeps $40 within the original funding string might look something like this:

From:   Original Account           $-100

To:       New Account                   $60

            Original Account             $40