Hey @felix-mueller,
thanks for your reply. I now want to create a simple html form that always reads a boolean and submits it as variable general to the selected user task via the complete task REST API call.
Since I might have multiple user tasks expecting a boolean result in a workflow, I want to immediately store the value in general to an individual variable x via output parameter, but get error messages I do not understand. I wrote an independent question for this at Conditional flow expression using just created output parameter.
I hope I can use user tasks with REST complete calls and immediate mapping via output parameter and directly afterwards a conditional flow expression, because that would be a really nice general solution for covering all user tasks with one external form.