You can add multiple tasks in bulk with ThunderTask, this is how you do it:
Click on the "New Task" button in the header and the "Add new task" overlay should appear. Then click on the link which says "Add multiple tasks" and the task input field should get a little bigger.
You can now add multiple lines of tasks. You can even start each line with a hyphen, it will be removed once you hit Save. If you hit the Save button, every line will be added as a seperate task.
Adding multiple tasks at once is a great way to import lists of tasks you might already have from other tools or text files.