Copying files from an inherited nuget

I've developed a custom NuGet which uses DotNetProjects.DotNetSiemensPLCToolBoxLibrary. DotNet library includes external dlls that are copied into the output directory following these statements:

<Content Include="..\externalDlls\libnodave_jfkmod.dll"><Pack>true</Pack><PackageCopyToOutput>true</PackageCopyToOutput><CopyToOutputDirectory>Always</CopyToOutputDirectory></Content><Content Include="..\externalDlls\libnodave_jfkmod64.dll"><Pack>true</Pack><PackageCopyToOutput>true</PackageCopyToOutput><CopyToOutputDirectory>Always</CopyToOutputDirectory></Content>

However, when my custom Nuget is used in another project, DotNet dlls are shown on project tree but not copied into the output directory.

nuget use example

If I set manually that these dlls will always be copied into output directory it works. It is posible to do so in the .csproj of my custom nuget?.