[SOLVED] Provider/Client invoice label

Hi all,

I am looking for a way to add a customized column (label) to the provider/client invoices. In this specific case it's a label named currency unit. I would like to get that information for each listed invoice when I access that specific screen (please see attachment named "list of current columns").
For this I have been exploring the "to manage" feature under the option "select columns to display" (please see pic attached named "to manage feature").
The thing is, when I create a new label (as in pic attached named "new label") I can't find a way of selecting that new column to my main screen.
I must be doing something wrong here.
Can you please help me?
Thank you in advance!