If I understand your request you would like to edit existing issues including those with custom fields. An example message to update assignee, priority and 2 custom fields for the issue QA-31 would be :
example input data
There are a lot of other great examples of JIRA REST API available from here:
Hey Community mates! Claire here from the Software Product Marketing team. We all know software development changes rapidly, and it's often tough to keep up. But from our research, we've found the h...
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