When a manager leaves on vacation, there are several methods to transfer his pending requests:
1) The manager transfers his approval responsibility to a person of his choice before his departure. To do so, he needs to click on the number of people he supervises in the "Status" block.
2) The administrator goes to the manager employee’s file and click on "Transfer approval permission".
Good to know: You can choose the scope of the people proposed as the new supervisor in the permission configuration (Administration > Parameters > Permissions). For that purpose, modify the "Employee scope" at the level of the parameter "Information - Choice of supervisor".
3) The administrator can transfer pending request of a manager via Manage > Transfer of requests
Warning: You cannot transfer those rights temporary. Therefore, when the Manager is back from holidays, you need to realize the same operation the other way round.