Users with the Manage Workflows role can administrate the workflow delegation. Go to Configuration > Workflows > Workflow Delegation to display a table with all the delegations.

As an administrator, you can:

• Create a delegation for any source and target user in the partition.
  You can do this also for inactive users and this way delegate approval tasks of users who have left the company.
• Delete or terminate ("EndDate") any existing delegation.
• Create a filter that will narrow down the list of users available for delegation.

Create a User Filter

You can specify, which users will be available to the user who creates a delegation. For example, only users with the same business role can be selectable.

1. Go to Configuration > Calculation Logic > Generic Logic and create a new logic.
2. Set its Nature to Workflow Delegation User Filter.
3. Define the filter in the logic element.

 The following code snippet returns all users with the same business roles as the current user:

def myBizRoleNames = api.user()?.businessRoles*.uniqueName
if (myBizRoleNames == null) myBizRoleNames = []
//if (!myBizRoleNames) {
  //what to do when there are no bizRoleDefined?
//}
return Filter.and(*myBizRoleNames.collect {
  Filter.some("businessRoles", Filter.equal("uniqueName", it))
})

The following IF statement excludes defined users:

if (api.user().loginName != "admin") {
  return Filter..... //as above
}