Add an indicator to the Footprint Properties dialog that the 3D model file doesn't exist (or there's some other problem)
Having a file path for 3D model in every footprint in the official library even when there's no corresponding 3D model file may be a technically good idea, but for usability, especially for newcomers, it's confusing. Many times someone has wondered in the user forum why they can't see the 3d model even though it should be there.
This would be helped if there was some visible indicator in the Footprint Properties dialog's 3D Settings when the file doesn't exist or there's some other problem.
There are many possibilities. My own proposition would be to have an extra column in the "3D Model(s)" table. It would have an icon showing the status of the file: OK, warning, error (as they often are, a green tick mark, a yellow triangle with exclamation mark, a red circle with exclamation mark). Hovering over or clicking that mark would show the problem explanations. Warning could be shown if the model exists and can be read and rendered but has some problem (for example there's a STEP model but the model is scaled). Error would be shown if the model doesn't exist or can't be read or interpreted or rendered.
Application: Pcbnew Version: (5.99.0-791-g06c979dfa), release build Libraries: wxWidgets 3.0.4 libcurl/7.66.0 OpenSSL/1.1.1d (Schannel) zlib/1.2.11 brotli/1.0.7 libidn2/2.2.0 libpsl/0.21.0 (+libidn2/2.1.1) nghttp2/1.39.2 Platform: Windows 8 (build 9200), 64-bit edition, 64 bit, Little endian, wxMSW Build Info: Build date: Jan 24 2020 06:58:39 wxWidgets: 3.0.4 (wchar_t,wx containers,compatible with 2.8) Boost: 1.71.0 OpenCASCADE Community Edition: 6.9.1 Curl: 7.66.0 Compiler: GCC 9.2.0 with C++ ABI 1013 Build settings: KICAD_SCRIPTING=ON KICAD_SCRIPTING_MODULES=ON KICAD_SCRIPTING_PYTHON3=OFF KICAD_SCRIPTING_WXPYTHON=ON KICAD_SCRIPTING_WXPYTHON_PHOENIX=OFF KICAD_SCRIPTING_ACTION_MENU=ON BUILD_GITHUB_PLUGIN=ON KICAD_USE_OCE=ON KICAD_USE_OCC=OFF KICAD_SPICE=ON