Hello ,
I went ahead and double checked for you. It appears that this feature request is still under consideration by the developers. However, you could achieve this result by having two widgets blueprints. A “Master widget” blueprint and a the widget blueprint that you would like added to the viewport.
To achieve the “One time Construction”, you would use the Master widget’s construction event (This is added to the screen once and left there). NOTE: This is the widget blueprint that you will use the “Add to Viewport” node on.
To achieve the “Construction on add to viewport”, you would use the Widget blueprint that you would like add to the screen’s construction event. However, instead of adding it to viewport, you would simply add it as a child to the Master blueprint and then remove it from parent as normal to remove it from the viewport.
I hope that this information helps.
Make it a great day