I don't think poser can save these kind of poses directly - you'll have to manually edit the pz2 file.
Just create a text file that goes as follow (without the lines at top and bottom:

----------------------------------------------------<br></br>{<br></br><br></br>version<br></br>    {<br></br>   number 4.01<br></br> }<br></br><br></br>actor rToe:1<br></br>       {<br></br>              off<br></br>      }<br></br>actor lToe:1<br></br>   {<br></br>              off<br></br>      }<br></br>actor rFoot:1<br></br>  {<br></br>              off<br></br>      }<br></br>actor lFoot:1<br></br>  {<br></br>              off<br></br>      }<br></br>actor rShin:1<br></br>  {<br></br>              off<br></br>      }<br></br>actor lShin:1<br></br>  {<br></br>              off<br></br>      }<br></br>}<br></br>-------------------------------------------------

then save it with a .pz2 extension inside of a folder in your pose library and it should be done (at least it work in P4, but P5 should be fine as well, whereas i couldn't tell about P6).
Hope this help.
Grim