I paid off part of my daughters FedLoan obligations in 2018. I paid off $26,648. Is any or all of this deductible?

First, were you legally obligated to pay the loan? For example, were you a co-signer on the loan? If not, then you have nothing to claim here. Otherwise, the portion of interest that you paid as reported on the 1098-E can be deducted by you.

I was 76 years old in 2018, when i paid this loan.

No, none of the loan payoff is deductible.  The student loan is a personal loan and is not reported on or deductible on a federal tax return.  Only the student loan interest paid can be reported on a tax return.