is there an option to make the completed tasks should go down the list

[ramanamuttana 0]

in the above image  , once i completed the task or check the task is completed  , then  it should go down the list , inspite of staying at its position , is there any option for that 

[agsteele 2,374]

No, that option does not exist.  You have to manually drag the item down or just delete it if it is no longer required.

[Jon/t 636]

I tend to use the home screen widget or the slide out task bar for managing tasks because of this reason. When a task is completed it disappears from the list.