How to update Query issue multi linker custom field using REST API

[deevant07]

I have a custom field of type "Query issue multi linker custom field" which needs to be updated from REST API.
Facing 2 problems: using the rest path http://localhost:8080/rest/api/2/issue/ND-1

I am able to update custom field with one value if the issue is not assigned to any value but if the value is already assigned it is not allowing to update.
I am not able to update multiple values for the custom field.

Please help on this with appropriate REST API

[stevegoossens]

I also cannot set multiple values for this type of customfield as it appears to only accept string types, and no variations of list/arrays or json is accepted (string-wrapped objects can succeed to get an issue created, but the field (even though requires a value) has no values set in the resulting ticket.

Single value as string succeeds:

{"fields":{"description":"Creating a ticket via REST API\nMulti-line","reporter":{"name":"[email protected]"},"customfield_10351":{"value":"P4"},"assignee":{"name":"[email protected]"},"customfield_10286":[{"value":"Other"},{"value":"Cloud"}],"customfield_10052":"2016-03-25T22:41:00.000+0000","customfield_10442":"Service impact is something something","summary":"REST API test","customfield_10314":[{"value":"OTG-Foundation"},{"value":"OMG"}],"customfield_12601":"SERVICE-138","customfield_10312":[{"value":"Test"}],"customfield_10474":[{"value":"User"},{"value":"Zenoss"}],"project":{"key":"OPS"},"issuetype":{"name":"Incident"}}}
response status code = 201
{"self": "https://jira-test.dev.bbc.co.uk/rest/api/2/issue/884288", "id": "884288", "key": "OPS-160054"}

Array of strings fails:

{"fields":{"description":"Creating a ticket via REST API\nMulti-line","reporter":{"name":"[email protected]"},"customfield_10351":{"value":"P4"},"assignee":{"name":"[email protected]"},"customfield_10286":[{"value":"Other"},{"value":"Cloud"}],"customfield_10052":"2016-03-25T22:41:00.000+0000","customfield_10442":"Service impact is something something","summary":"REST API test","customfield_10314":[{"value":"OTG-Foundation"},{"value":"OMG"}],"customfield_12601":["SERVICE-138","SERVICE-747"],"customfield_10312":[{"value":"Test"}],"customfield_10474":[{"value":"User"},{"value":"Zenoss"}],"project":{"key":"OPS"},"issuetype":{"name":"Incident"}}}
response status code = 400

Array of single key-pair dicts fails:

{"fields":{"description":"Creating a ticket via REST API\nMulti-line","reporter":{"name":"[email protected]"},"customfield_10351":{"value":"P4"},"assignee":{"name":"[email protected]"},"customfield_10286":[{"value":"Other"},{"value":"Cloud"}],"customfield_10052":"2016-03-25T22:41:00.000+0000","customfield_10442":"Service impact is something something","summary":"REST API test","customfield_10314":[{"value":"OTG-Foundation"},{"value":"OMG"}],"customfield_12601":[{"key":"SERVICE-138"},{"key":"SERVICE-747"}],"customfield_10312":[{"value":"Test"}],"customfield_10474":[{"value":"User"},{"value":"Zenoss"}],"project":{"key":"OPS"},"issuetype":{"name":"Incident"}}}
response status code = 400
{"errorMessages": [], "errors": {"customfield_12601": "Operation value must be a string"}}

The schema for the customfield appears to only allow set operation:

        "customfield_12601": {
            "operations": [
                "set"
            ],
            "required": true,
            "name": "Core Service Impacted",
            "schema": {
                "items": "string",
                "customId": 12601,
                "type": "array",
                "custom": "ru.mail.jira.plugins.lf.queryfields:mailru-multi-linker-field"
            }
        },