If I incurred a Medical Expense at the end of 2020 but paid the bill in 2021 can I add these expenses to my total 2020 Medical Expense deduction?

[DoninGA]

No.  Only the expenses paid in 2020 with out of pocket funds can be entered on the 2020 tax return.  You can enter the expenses paid in 2021 on your 2021 tax return to be filed next year.