Determine the user's multi-instance task

Now I want to implement the function of countersigning, but I want to start the multi-instance task directly after setting multiple alternate users/alternate groups on userTask when I draw the flow in flowable, where the multi-instance parameter collection will be obtained from the data set by me. As far as I know, it can only be set by means of variables, by passing parameters when starting the process, or by listening to the process or task. This is not in line with my business implementation. I wonder what other options there are?