The path to an manifest file describing all of the asset bundles used in the build (optional).
When you call BuildPipeline.BuildAssetBundles to create your AssetBundles, it also creates a manifest file describing the bundles produced. You can assign the path to this manifest file to assetBundleManifestPath to ensure that a player build does not strip any types used in the asset bundles from the build.
BuildPipeline.BuildAssetBundles creates the manifest file in your AssetBundle output path, with a filename matching the parent directory name and ".manifest" as its extension. You can specify the path to the manifest using an absolute path or a path relative to the project directory.
You do not need to set this property when you generate asset bundles using the Scriptable Build Pipeline package.
Additional resources: BuildPipeline.BuildAssetBundles, AssetBundleManifest.