You could alternately also define an approval process utilizing the "Kanban State" field. It is the colored dot (Grey, Green, Red) on a ticket (top right) and is also visible on the kanban and list views.

The description of these color/ state can also be customized from helpdesk > Configuration > Stages

Tickets needing approval can be marked as Green and the approver can approve by moving ticket to next stage. Once stage is changed, the color/ state automatically changes to grey (normal/ in-progress).

Unapproved tickets can be marked as "Red/ Blocked' by the approver and left in the same stage for further action.

Tickets can be filtered by Kanban State, and an approver can save 'filter Kanban State is Green' as Favorite so they can view their actionable tickets.

Create an Activity Type called "Higher Level Approval" and train Helpdesk Users to schedule the approval when needed.

Activate Developer Mode and visit Settings --> Technical --> Discuss --> Activity Types:

Helpdesk User:

Ticket will then show:

Manager will then see: