Configuration of popups takes time. When creating a web map its a common need to enable/disable/re-enable popups as we determine the look and feel and behaviour that our end users are looking for. When a popup has been configured (fields turned off or on, formatting applied, alias's edited....) the configuration is blown away when you disable the popup, without any kind of warning. When you re-enable the popup you have to reconfigure it ... again...and again.
In addition - if popup configurations persist in web map layers' disabled popups, they should also then persist in the Web AppBuilder Layer List widget where the end user can enable the layer's popup. This would provide a much better authoring experience and end user experience.
Please make popup configurations persist after the author disables a popup. The configuration should persist when the popup is enabled at a later time.