Moving activities from a Team Lead's route to an Assisting Team Member's route from a plugin

We use the Assisting Activity / teamwork feature. The Team Lead (crew resource type) receives all the activities, and the Team Member (field resource) is assigned as an assistant.

When the Team Member submits a form plugin on their own route, we want the plugin to move all of the Team Lead's pending activities for the day onto the Team Member's route.

We would like a standard, supported approach that does not need an external server. Optionally, it would also work offline on mobile.

What we tried, and the result

REST API using getAccessTokenByScope (scope urn:opc:resource:fusion:<instance>:field-service-common/use