Hello. If it were up to me, I would use these terms:
"The transaction will post tonight" = "La transacción será registrada hoy por la noche."
You could also use "La transacción será publicada hoy por la noche."
"In Quicken, there are options to mark a transaction as reconciled or cleared." = "En Quicken, hay opción de marcar una transacción como reconciliada o aprobada."
You could also use "En Quicken, hay opción de marcar una transacción como reconciliada o aceptada."
My reasoning is the following: "to post a transaction" means basically that a transaction will be registered in your account, and you could also use published in Spanish.
And for "cleared", which basically means that you looked at the transaction, and approved it, ( i.e. because you did make that expense ), or accepted the charge (for example, because you did buy something for that amount), I would use "aprobar" or "aceptar", because even though "to clear" can mean "aclarar" in Spanish, in this context, "to clear" means something closer to "approve" or "authorize".
Hope this helps, buena suerte!