We would want to sync custom fields/system fields between a existing ticket & its associated linked ticket created in remote instance .

Usecase :

Lets say we have two Jira instances A & B . We have mechanism where we can create a ticket from instance A in Instance B . The ticket created in Instance B is visible in Instance A as under issue links .

Now we want to sync the source ticket (Instance A ) with its associated Linked issue (Ticket from Instance B visible in instance A under issue links section).