Example 9 - Setting field value using Jira REST API
Although Power Custom Fields does not currently have REST API support, it is possible to set values for fields using Jira’s REST API. To do this, use the following syntax:
For multiple values fields:
{"label1":"","value":"10000"}#|#{"label2":"","value":"10001"}
For single values fields:
{"label": "Some label", "value": "some_value"}
See More