Plug-ins and Scripts Installation in Windows and Linux

In Windows

Plug-ins (.exe, .py)
N.B.: Make sure the exe files are not installers. They must be the plug-ins them self's.
%programfiles%\GIMP 2\lib\gimp\2.0\plug-ins (Global installation)
%userprofile%\.gimp-2.x\plug-ins (Current user)

Scripts (scm)
%programfiles%\GIMP 2\share\gimp\2.0\scripts (Global installation)
%userprofile%\.gimp-2.x\scripts (Current user)

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In Linux

Plug-ins
/usr/lib/gimp/2.0/plug-ins (Global installation) May not be true to all distros
/home/*user*/.gimp-2.x/plug-ins (Current user)

Scripts
/usr/share/gimp/2.0/scripts (Global installation) May not be true to all distros
/home/*user*/.gimp-2.x/scripts (Current user)