To concatenate intro and outro to my screencasts, I use ffmpeg to stitch the videos from the command line. It is faster and easier than using the ScreenFlow.
brew options ffmpeg
brew install ffmpeg --with-fdk-aac --with-ffplay --with-freetype --with-frei0r --with-libass --with-libvo-aacenc --with-libvorbis --with-libvpx --with-opencore-amr --with-openjpeg --with-opus --with-rtmpdump --with-schroedinger --with-speex --with-theora --with-tools
