You can update nomination details for all your existing schemes at once clicking on the links provided by the RTAs below:
CAMS and Karvy
How to Switch/SWP? (Mutual Fund Scheme Switch / Set up a Systematic Withdrawal Plan)
Where can I check my Mutual Fund holdings? / Where can I check my MF holdings? / Where can I check my Mutual Fund Portfolio?
How to Invest in Mutual funds through Kotak Securities?/ What is the new flow for Investing in Mutual Funds?
How to STOP/Modify your Mutual Fund/MF SIP?