Great question from the road today! With all the changes over the past couple years it's hard to keep track, but we're back to no tickets to enter the building - tickets required for Permanent Exhibition only. If you have a 'Daniel's Story' visit, you do not have/need tickets; therefore, no reservation for a 'timed entry' either.
From USHMM website 3.14.23:
'To help reduce the risk of transmission of COVID-19, the Museum is reopening on a limited basis with new visitor requirements and safety measures in place. Free timed-entry tickets are required to enter the Museum’s Permanent Exhibition only. Tickets are not required for Daniel's Story and other special exhibitions.'