Under the hood, this operation overwrites the engine modules by the files from verge3d/build folder, namely, Verge3D runtime v3d.js and optional compatibility modules ie_compat.js (enabled by IE 11 checkbox) and webxr-polyfill.js (enabled by Legacy VR checkbox in the app creation panel). If you choose so, this operation will also overwrite the selected HTML/CSS/JavaScript files and the icons folder media by the files from verge3d/manager/app/Standard folder.