Because of unique identifiers you can't just rename the new block to be the same name and have it take the place of the old one. You will need to go into the playbook and delete the old block in the playbook and drag the new one into its place.

Hi ddiserens,

Thanks for the reply. I am more concern about the input and output of the block which were used in diffrent blocks or actions which may need to check and will have to test entire flow of the playbook for any impact.

Last option will be the one you suggested. I was looking for any trick or way through i can replace the block with the new one without impacting the playbook.

Regards,

Laxmikant

If the block just has minor changes you could copy the new stuff from the block and paste it into the old block. 

No the changes are major...i guess i will follow the steps you suggested earlier