Any package that appears under your project’s Packages folder is embedded in that project. Typically, when you create a new package, you embed it in your project while you are developing it. When it is ready to be shared with other users and tested in other projects, you can publish it to a scoped package registry.
独自のカスタムパッケージを作成する方法に従って、Packages フォルダー下のフォルダー内にパッケージコンテンツを作成することで、新しいパッケージを埋め込むことができます。また、Package Manager Scripting API を使って既存のパッケージを埋め込むこともできます。詳細は、パッケージをプロジェクトに埋め込むを参照してください。
Embedded packages do not appear in the project manifest as a dependency; however, if you embedded a version of an installed package using the Client.Embed method, your project manifest still lists the dependency on the original installed version. In that case, the package on disk takes priority over the version of the package listed as a dependency, so it does not need to be removed from the project manifest. For example, if the project manifest specifies a dependency on version 1.3.1 of the com.unity.example package but the project also has an embedded package with that name, the Package Manager uses the embedded package, regardless of its apparent version, instead of downloading version 1.3.1 from the registry.
It is your responsibility to track the content of your embedded packages, and any changes you make to it. If your Unity project is under source control, add packages embedded in that project to the same source control.