Yes, any amount of advance payments of the premium tax credit that you had to pay back can be included in medical expenses. You would report the amount you had to pay back as a medical expense in the "Deductions and Credits" section of TurboTax.

Please see IRS Publication 502 for more information. 

I owe the Obamacare subsidy back. Can I take the amount  on my 2019 tax return, as a medical expense on my 2019 tax return? I entered my 1095A under the Medical expense deduction as directed yet the amount shows up as zero and I still owe $10,000?

Yes, you can deduct the repayment amount you paid.

Per IRS Any amount of advance payments of the premium tax credit that you did have to pay back can be included in medical expenses.

In order to affect your return, you need to itemize your deductions and the amount of medical expenses must exceed 7.5% of your adjusted gross income. 

I already submitted my income tax and charged a penalty/interest. I know this has something to do with Obamacare credit. Why did Turbotax not mention to include the advance premium tax credit as a medical expense? It would have reduced my tax substantially!