You can instruct an order to continue to work after normal trading hours have ended by enabling Outside RTH (outside regular trading hours). You can manage the Outside RTH attribute as a default order preset, and also on a per order basis.
Watch a brief animation below to see exactly how to set Outside RTH for an order, or how to set is as the order default for a specific asset type.
Note: If you want Outside RTH enabled by default, you only need to define the preset in ONE platform. It is then automatically applied across all of your trading platforms.