There is no out of box substitution feature in Bonita BPM 6.2 but you can mage it using an adeguate actor filter.
Let me explain with a real use case:
user1 is the manager of group1 so he has the rights to approve all the purchase orders coming from his managed group
user2 has the same roles for group2
user1 decide to get holiday for incoming two weeks. he can update information about in doesn't matter source (you can manage it using a new Bonita process calling it Substitution that can allow every user manage their own holiday planning)
your custom actor filter would retrieve information about substitution from this source and re-assign the task to user2. Don't forget that via API you can force re-execution of actor filter, it means that you can re-assign also task already instatiated.
User1 could manage his substitution period: can delay it, delate, enlarge...
You can easily provide information about task assigned to users belonged to a team manager using API. You can develop a form using Bonita Form Builder where show a list of task. Below an example how retrieve user managed by user1
Bonitasoft empowers development teams with Bonita, the open-source and extensible platform to solve the most demanding process automation use cases. The Bonita platform accelerates delivery of complex applications with clear separation between capabilities for visual programming and for coding. Bonita integrates with existing solutions, orchestrates heterogeneous systems, and provides deep visibility into processes across the organization.