But the Adjusted Gross Income shown on my Form 1040 for 2020 has not been reduced for the Excess Deductions reported in Box 11A of my Schedule K-1 information.
The reason you are not seeing the deduction is that TurboTax does not know precisely how to handle the figure in Box 11A since the Regulations specify three different categories of excess deductions:
1) Amounts allowed in arriving at AGI
2) Non-miscellaneous itemized deductions
3) Miscellaneous itemized deductions
Therefore, you need to inquire as to the exact nature of the deduction(s) taken by the estate.
If the deductions are all classified as miscellaneous itemized deductions, then you will have no deduction since these types of deductions were eliminated by tax reform (the TCJA).
Deductions that are non-miscellaneous itemized deductions should be entered on Line 16 of Schedule A while the deduction of amounts allowed in arriving at AGI should be entered on Schedule 1.
Note that non-miscellaneous itemized excess deductions should appear in Box 11B of a K-1 (1041) for the 2020 tax year and the IRS is still in the process of finalizing drafts of some 2020 forms and schedules.