Mon - The Scheduler Task List consists of Tasks. If you select one Task from the list of Scheduled Tasks and click 'Edit selected', you can change the name of each Task by changing the text in the Name field at the top.

If a Task consists of one or more Chained Actions (sequences of actions), you can edit the name of each Chain Action by clicking the Edit button displayed under the Edit Task dialog 'Action'.

Whether you choose to test or not, each time you add an Action you will initially see the Action listed only in the middle of the Edit Task dialog, but no Task Name will be assigned until you click OK to dismiss the Edit Task dialog. After you fully dismiss the Edit Task dialogue, you will see the Name assigned to the Task appear in the Scheduler configuration dialog in the Scheduled tasks pane.

Thanks Thomas :D

Unfortunately I still could not find the dialogue which I can set the task name for Chain Action - -'
So, I captured the screen here.
The screen in page 3 and 4, there has no option which I can set the task name.

I planed to set the schedule to update the daily data from many sources. It may be difficult if it shows only 'File action on ....." in 'Actions' box (page 3) for all actions.

Naruemon, correct me if I am wrong, you are trying to change name of actions which are not "Chain actions". At the current moment in time you can't change the name of any actions other than chain actions.

I have attached a PDF document which states a normal workflow of how to define and edit schedule tasks. The attached document should help you better understand how Scheduler/Service tasks work and scheduled.

I would like to add to my previous reply, that we are in the future going to change the dialogs of the Scheduler/Service to help make it easy to schedule tasks.

Thanks Mustafa ^^

In 2.8 we have added the ability to give each action a custom title which should help you achieve what you are trying to do.

Thanks for the update :D