How can we move a process instance currently stuck at a timer/ user task to a specified task/activity?
What do you mean with ‘stuck’ here? Has the activity somehow failed?
If you’re looking for migrating instances from one state to another, you can have a look at https://github.com/flowable/flowable-engine/blob/master/modules/flowable-engine/src/main/java/org/flowable/engine/ProcessMigrationService.java