The Project Leader's Approval Required option is found only in the root project of a Project Structure. This article talks about the purpose of enabling or disabling this feature, in detail.

  • Enable this option to require the project leader to approve all time and expenses entered against this project
  • If this option is disabled, time and expense sheets that include data for this project only will bypass the project leader in the approval process
  • To act as an approver, the project leader must be included in the submitting user's approval path

This feature is useful when the timesheet users' approval path is set as Project Leader (being the first level in the approval path) and Supervisor (being the second level in the approval path), but not all the project needs a project leader's approval and instead could just be approved by the supervisor directly, skipping the project leader's
approval.
In the above scenario, projects those need or should have a project leader's approval always, will be set with Project Leader's Approval Required option enabled and the
projects those don't need a project leader's approval will be set with Project Leader's Approval Required option disabled.