I am trying to reorder an off-panel widgets in WAB, I am clicking the widget and dragging it to the location I want between two other widgets, but I do not see the Red line appear.
There is no support for re-ordering off panel widgets, That is only supported in controller widget like the Side panel controller and the header controller.
Just to update this thread, in the April 2018 update of Web AppBuilder in ArcGIS Online, you can re-order widgets added in the app UI by clicking and dragging to re-arrange their order.
