Replying to my own post:
I found another alternative that may be more simple.
TurboTax allows the "Payer's information" (ie. the bank name) to contain a long text description. I can enter the 2024 accrued interest income as box 1 for the 1099-INT, and append an explanation to the Payer's information.
Payer's information: "Bank of Montreal (This value represents the accrued interest from 2024, interest accrued from 2023 was declared on my 2023 return, the NR4 states the total interest for 2023 and 2024)"
This avoids trying to get TurboTax to accept the NR4 and adjust for previous accruals (and do math under the covers that may or may not be accurate).
