Any subscriber fields, custom fields, and list subscriptions can be updated during execution of a trigger.

JS Code

The tm.api method provides access to the full range of Taguchi APIv4 functionality, and can be used as follows:

var tm = require('tm');

exports.handler = function (event){
    tm.api('subscriber', 'update', {
        record_id: event.subscriber.id,
        data: {
            custom: {
                sampleField: "some sample data"
            }
        }
    });
}

Reference

For more information about advanced triggers, see the Advanced Trigger Reference.