In your project, click on the TASKS tab.
When you select a task list, all tasks in this task list will be selected and all tasks can be modified, using the Tasks selected toolbar at the bottom of the page:
Furthermore, individual tasks can also be multi-selected:
The following modifications can be made to the task lists of tasks:
This option allows you to Mass edit tasks:
Select the start date of all tasks.
Select the duration of the tasks.
This is automatically filled when the duration is entered.
Assign to project members
Assign the tasks to members.
Select the priority of that tasks.
Select the status of all tasks.
This option allows task(s) to be moved to another task list:
This option allows to copy a task or multi-selected tasks:
This option allows you to delete a task or multi-selected tasks:
This option will clear the selected tasks.