I would like to suggest a translation in Spanish for this word. This is "línea adicional".
I corrected this a few moments ago in the English-Spanish dictionary. Now the translation reads línea adicional, línea auxiliar. Please notice that changes take some time to be visible on the website. As for adding a sense for accounting, it seems like this entry used to have the sense financial record, but that was changed to the music one (hence the error in the Spanish translation). I will forward this thread to the team that manages the English base dictionary so they evaluate the possibility of restoring the financial record sense.For the description: (music: line above or below staff), the translation is indeed linea adicional or linea auxiliar but there should also be a translation for "ledger" line" as an entry in the accounting books.