Order discount system

Hi,
I want to auto update order total when It is discount apply or add-remove item in order
how can I solve this problem, Is there a plugin for this?

I'm not aware of a plugin for it.
There is a setting that is False by default.  You can try setting it to True:
ordersettings.autoupdateordertotalsoneditingorder

However, there may be some concern of how well it works:
https://www.nopcommerce.com/en/boards/topic/92828/problem-in-edit-detail-of-order-from-backend
https://www.nopcommerce.com/en/boards/topic/30188/recalculate-order-total#286404

thanks to comment.
i tried this method but, not working.
When I add item not working, Or does this feature not exist or should it be developed?