How to lock task number updates after initial creation of tasks

Summary

How to lock task number updates after initial creation of tasks

Content

Has anyone in this group attempted to lock task number updates in project financial management after initial creation of tasks?

Essentially, we would want the users to create a project and add tasks and thereafter these tasks will require to be made read-only. But they should be able to create brand new tasks.

I have had a look at privileges in project job roles and I couldn't spot a task update privilege I could remove.

I have also explored page composer functionality but these are limited to boolean values [true, false]. This means you can either edit or the field is read only.