Source : https://tmux.github.io
Download : http://www.qnapclub.eu/index.php?act=detail&qpkg_id=395
x64 version : http://www.qoolbox.fr/Tmux_2.3.0_x86_64.qpkg.zip
Note :
once installed tmux is linked to NAS $PATH can be executed like all command
About :
What is a terminal multiplexer? It lets you switch easily between several programs in one terminal, detach them (they keep running in the background) and reattach them to a different terminal.