Hi
You should look through the "General Discussion" If I remember, there was a post about "tailing" the map together in order to get good quality map,
If you are new, I suggest to go through the posts and see what you can use in your project
If you would like to have existing\proposed conditions you should have 2 layers (1.existing, 2. existing + proposed, OR it depends on your project for instance if you are going to demolish some of the existing buildings then 1.existing, 2. existing-after demolition + proposed)
[[[ If you will have 1.existing, 2 proposed then in a WebScene you will have one or another ]]]
In order to get a "slide bar" when you export to WebScene name those 2 layers [existing, existing+ proposed] with the same name
To start the project check the attachment
[ATTACH=CONFIG]32476[/ATTACH]