Before taking the Google Cloud Professional Security Engineer exam, you should read the documentation at the following links. This list contains topics that were not covered anywhere else in this learning path.

About VM metadata
Automate user provisioning across cloud apps
Best practices for Cloud Audit Logs
Control access to BigQuery resources with IAM
Create short-lived credentials for a service account
Help keep your Google Cloud service account keys safe
Image management best practices
Implement data residency and sovereignty requirements
Introducing Risk and Compliance as Code
Introduction to the Organization Policy Service
Limit the amount of content inspected (only this section)
Maintain a vulnerability management program (only this section)
Managing users programmatically
Overview of Access Approval
Packet mirroring use cases (only this section)
Policy Intelligence
Pseudonymization
Security Command Center overview
Service account impersonation (only this section)
Setting up OAuth 2.0
Signing in users with SAML
Super administrator account best practices
Uniform bucket-level access
Use password policy
Workload identity federation

Required Reading for Google Cloud Professional Security Engineer Exam