KACE Product Support

In the image below, I want to make staff only the Approvers. We have over 1000 staff, so cannot put these in individually and the User's Managers are not set in the USers Menu. This means the option of Submitter's Manager will not work. Any suggestions how I could make this work? What I am trying to achieve is as follows:

I have already restricted the Approvers to staff only but do not know how to make that entry in the Approval Step 1 box (see image below)

1. User submits the IT Hardware Request form
2. On Save, an email goes to the Approver, who could be any number of people i.e. Head of Department, Line Manager, Budget Holder etc.
3. Approver receives an email, stating the ticket number he/she needs to approve
4. Approver logins in a puts a tick in the Approval box.
5. On Save, email goes to technician's team, stating that approval has been given and they can now proceed with purchase of requested equipment

It is the email to the Approver (Approval Step 1) that I am struggling with, especially as the Approver is not necessarily the submitter's line manager.

Regards

Fola