The offset distribution satisfied the loan, so the money that you are putting into the plan as "repayments" are actually rollover contributions to the plan, not loan repayments. You only have until the extended due date of your tax return to make rollover contributions to reduce the taxable amount of the offset distribution. You might want to file a request for a filing extension to ensure that the deadline for making rollover contributions is extended beyond the regular filing deadline of April 18, 2022 to October 17, 2022. (Filing your tax return by April 18, 2022 will also extend the deadline for making these rollover contributions, but you'll have to file an amended tax return if you make additional rollover contributions with respect to the offset distribution between the time you file and October 17, 2022.) After October 17, 2022 you will not be able to roll over any other amounts of the offset distribution. These remaining amounts will be subject to tax and an early-distribution penalty. Ideally you would be first rolling over amounts of the distribution from the traditional 401(k) account since portions of the distributions from the Roth 401(k) will be free of tax and penalty.
In TurboTax you'll need to indicate the amount of this distribution that was rolled over.
401(k) plans have is no equivalent to Form 5498. The new 401(k) plan reports nothing to the IRS regarding receipt of the rollover. It's probably more common that people roll an offset distribution over to an IRA rather than an employer plan, in which case the Form 5498 provided by the IRA would code the rollovers as rollovers of an offset distribution.
