Integrating with Process Cloud: how to add attributes while submitting a task

Summary

We don't know how to submit attributes to a process instance while submitting a task from a visual builder web application.

Content

Goal
We'd like to use Process Cloud to control our business process and include both human- and automated tasks. We however don't want to use Process Cloud's integrated webforms for human tasks, but use a webapplication built in Visual Builder instead.

Approach

1. We built a process in Process Cloud containing some human tasks and published it.
2. We built a webapplication in Visual Builder.
3. We succesfully integrated the published process in our webapplication and are able to:
   1. Start new process instances from our Visual Builder webapplication.