Pre-requisites:
'Admin' permission on the project template where a system task needs to be created.
The steps to create a system task for locking placeholder activities in a project template are as follows:
Follow the steps to create a system task for placeholders in a project template (steps 1-4).
Next, follow the steps to create a system task to lock placeholder activities in a project (steps 2-3).
Once done, click the 'Create' button to create a system task.