Hi @Ramesh_143,
Clarification question, do you see the 'Add to update set' in other areas and modules across the app, or is it missing everywhere.
I don't believe this is standard functionality. It's a handy utility and customization that lots of developers add to an instance to make things easier in the dev process.
It maybe that upon upgrading (depending on how you upgraded or refreshed your environment) it was overridden or ignored.
The good news, it is easy to add to your environment - check the following link from @Michael Ritchie who provides advice and the code required - Kudos
https://www.servicenow.com/community/developer-blog/add-to-update-set-utility-documentation-and-cust...
To help others (or for me to help you more directly), please mark this response correct by clicking on Accept as Solution and/or Kudos.
Thanks, Robbie
