Assuming you are correct that you are allowed to do the combination of revoking the election and claiming it on the 2020 return, you need to do things manually.

For the Asset Entry Worksheet, you enter the full amount of the Basis as Prior Depreciation/Prior Bonus Depreciation.  That will result in $0 of depreciation.

For the 3115, you need to manually calculate things, and enter the "§481(a) Adjustment" as an 'other' deduction.