When using the 529 plan as the qualified education expense, the savings bonds cannot be directly transferred to the 529 plan account. Instead, the bonds must be redeemed, and the proceeds deposited into the 529 plan account. The proceeds must be deposited within 60 days of cashing the bonds and within the same tax year. If the entire proceeds (principal and interest) are not contributed to the plan, then part of the savings bond interest would be taxable. Form 8815 is used to calculate the taxable amount.
this is the form for 2022
https://www.irs.gov/pub/irs-pdf/f8815.pdf
the amounts on lines 9,10 and 12 may change for 2023
if your MAGI (line 9) is too high for 2023 none of the interest is excludable
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