missing subcircuit schematic sheet reusability

Please add your _full_ KiCad version information to all bug reports.

This is from Help->About KiCad->Copy Version information.

Please do not link to external sites in bug reports. All information needs to be contained in the report itself.

Application: KiCad
Version: 5.1.4, release build
Libraries:
    wxWidgets 3.0.4
    libcurl/7.67.0 OpenSSL/1.1.1d zlib/1.2.11 libidn2/2.2.0 libpsl/0.21.0 (+libidn2/2.2.0) libssh2/1.9.0 nghttp2/1.39.2
Platform: Linux 5.3.11-1-MANJARO x86_64, 64 bit, Little endian, wxGTK
Build Info:
    wxWidgets: 3.0.4 (wchar_t,wx containers,compatible with 2.8) GTK+ 3.24
    Boost: 1.71.0
    OpenCASCADE Technology: 7.4.0
    Curl: 7.66.0
    Compiler: GCC 9.2.0 with C++ ABI 1013

Build settings:
    USE_WX_GRAPHICS_CONTEXT=OFF
    USE_WX_OVERLAY=ON
    KICAD_SCRIPTING=ON
    KICAD_SCRIPTING_MODULES=ON
    KICAD_SCRIPTING_PYTHON3=ON
    KICAD_SCRIPTING_WXPYTHON=ON
    KICAD_SCRIPTING_WXPYTHON_PHOENIX=ON
    KICAD_SCRIPTING_ACTION_MENU=ON
    BUILD_GITHUB_PLUGIN=ON
    KICAD_USE_OCE=OFF
    KICAD_USE_OCC=ON
    KICAD_SPICE=ON

I was told a KiCAD project archive is not really fully contained, ready to run on any other machine. One must add all kind of extra resources. I tried to add some library files I created and used for this example. I hope it is a complete example and can be executed on other systems. I suspect some library files must be placed in the KiCAD folder somewhere.

KiCad bug tracker has moved to Gitlab. This report is now available here: https://gitlab.com/kicad/code/kicad/-/issues/2596