You can control the PSA behavior of project tasks and project edit locking using the settings in the Task Management Settings custom setting.
Field
Description
Auto Create Task Assignments All or None
When true, errors are ignored when creating assignments or assignment milestones and that will cause project task assignment records to be created. When false, the whole operation is rolled back if any error occurs when creating assignments or assignment milestones and that will cause creation of project task assignment records. This option is ignored unless Automatically Create Task Assignments is true. The default value is false.
Auto Remove Task Assignments All or None
When true, errors are ignored when deleting assignments or assignment milestones and that will cause deletion of project task assignment records. When false, the whole operation is rolled back if any error occurs when deleting assignments or assignment milestones and that will cause deletion of project task assignment records. This option is ignored unless Automatically Remove Task Assignments is true. The default value is false.
Automatically Create Task Assignment
Indicates whether to automatically assign unassigned project tasks that belong to the same milestone as the assignment when assigning a resource to a project. For instance, when true and you assign a resource to a project with the Milestone field filled in, a project task assignment is created for that resource. The default value is false.
Automatically Remove Task Assignment
Indicates whether to automatically remove project task assignments when resource or milestone is removed or the milestone is no longer associated with that assignment. For instance, when true and the Milestone field on the assignment is cleared and that resource has no other assignments on that project with the same milestone, the project task assignment is removed. If the Milestone field on an assignment is changed and Automatically Create Task Assignments is true, the original project task assignment is deleted and a new project task assignment is created for the new assignment milestone. The default value is false.
Default Task Ordering
Controls the default way in which tasks are ordered on the Project Task Gantt user interface when it is initially loaded and when it is refreshed. The default value is "Start_Date_Time__c ASC NULLS LAST, CreatedDate ASC". This sorts the tasks by their start date if one has been set. If no start date is set, the tasks are sorted by the date on which they were created. If you change the value, the value that you enter must be valid after a SOQL ORDER BY clause.
Project Limit
Controls the maximum number of projects listed in the Show drop-down list in Project Task Gantt interface. The default value is 10000. If you have more projects than this you can set a value of up to 50000.
PT/PTA/PTD Require Lock Fieldset
Defines the API name of a field set you can optionally create on the project task, project task assignment or project task dependency object. The field set(s) should contain additional custom fields that can only be edited if the user has an edit lock for the parent project.
Track Points History Disabled
Indicates whether changes to the Points Complete and Points Remaining fields on a Project Task are recorded. When selected, changes to Points Complete and Points Remaining fields are not tracked.