We need to create a functionality in web app builder where
1. User selects few layers from layer list widget and creates a new set of layers out of them.
2. User then should be able to share them with other users who are loading the URL of web app builder .
3. Also at the same time if user closes the web app builder and reopens it he/she should be able to see the layer set already created.
I am trying to understand the feasibility of this functionality using Web app builder.
Thanks in advance.
Everything on your list are quite advanced things that I have not seen done yet. They would be possible for a very advanced developer though. I could not even begin to tell you where to begin on number one.
Since Robert is our communities most active developer (sharing with us anyway), I would have to agree with the difficulty level.
However, I would think one place to maybe start is a geoprocessing service if you have access to ArcGIS Server