Then you need to define a dependence in your app.json file so the new extensions is dependent on the old one.
List of dependencies for the extension package. For example: "dependencies": [ {"id": "4805fd15-75a5-46a2-952f-39c1c4eab821", "name": "WeatherLibrary", "publisher": "Microsoft", "version": "1.0.0.0"},{}].
Note: For dependencies to the System Application and Base Application these are no longer listed as explicit dependencies, but captured in the application setting as a reference to the application package. Must be filled in with the version number of the Application package. See application below.
Note: The version specified defines the minimum version for the dependency. At runtime and when downloading symbols, the latest version of the dependency satisfying the specified name, publisher and, minimum version will be returned. When runtime is set to 4.0 or earlier, use appId instead of id.