But if you do this be cautious that you plan knows it is a refund being recontributed not a new contribution. Otherwise the 1099-Q that you receive from your 529 plan for 2020 will be screwed up as it will show both withdrawals.
The simple option is to keep it in your bank account until the fall, assuming that the refund doesn’t exceed the remaining qualified expenses you will pay before the end of 2020 and just track your net expenses and withdrawals.