I’ve created an architectural walkthrough, but now want to migrate the whole project in to a mobile project for exporting to Gear VR. Is this possible to do without having to place all the meshes, etc, all over again?
By using the migration tool you should be able to migrate whole .uassets to a new project, including for architectural visualization and assets placed in a scene. While your whole project won’t be preserved, the assets and all of their dependencies should be and they you can reconfigure any of your project input or logic to be compatible with mobile Gear VR.
Alternatively, you can make a copy of the whole project and try reconfiguring the copy from there.
Hope that helps.
Documentation on migration can be found here, and more info about migrating whole maps here and here.