Defining Task Groups for Ad Hoc Workflows 
Use
If you want to define a workflow for an application object of a work item ad hoc, an associated task group must be defined.
Only certain tasks that already exist are to be used as activities in the workflow definition. These tasks must all be based on the object type of the application object. You collect these tasks in a task group and assign this to the object type.

A workflow is to be defined ad hoc for a work item that has a notification of absence (object type
Users who are allowed to create workflows ad hoc are only to use the tasks Process notification of absence and Display notification of absence. You therefore create a task group containing only the tasks Process notification of absence and Display notification of absence, and assign this task group to the object type
Procedure
To create a task group containing appropriate tasks for a particular object type, proceed as follows:
Result
When a workflow is created ad hoc, the task group appropriate to the object type appears in the tray My workflows and tasks in the Workflow Builder.