So Just to be on same you need to create approval system where new request or new record can be seen only by the PMO [Owner] or the person who has created this request from different department.
What i can suggest is use Power Automate to send link for approval and use item level permission inside your flow for maintaining the view permission of particular request
Step 1 : When Item gets created give read to creator or PMO and Approval Manager
Step 2 : Send Approval link to Manger for approval
Step 3: Once Approved remove permission of Manager and Add PMO for final Approval
Step 4 : Once All approval is completed : You keep who can view the record or remove who can't
Power Automate Is the way to go .....