Tasks details such as rates can be updated in bulk if required.   The import is matched on the task, if it is matches, it will update changes, if it doesn't it will add a new task.

Easiest process to update tasks is to export the existing task list to modify.   From the tasks dashboard (Tasks -> List Tasks) click the Actions button and select Export Tasks.

Update the downloaded task list csv with the required changes, ensuring the task names don't change as these are what the import tool matches on.   Once you are ready to upload the changes, click Import Tasks from the Actions menu.

Choose the updated task spreadsheet (must be in .csv format) and click Save.