There is no way to do that at the moment. But there is a c key which brings current line into command-line, which can be somewhat abused here. For example, if you make a menu using
the following K menu mapping will print process id from current line on status line:
:mnoremap K c<c-a><c-d>echo <c-e> | cut -f1 -d' ')"<c-a>!echo %S "$(<cr>
Right-hand side here is pretty much a sequence of command-line editing keys that add some prefix and suffix to the line.
This form might be more readable:
command printpid echo %S "$(echo %a | cut -f1 -d' ')"
mnoremap K c<c-a><c-d>printpid <cr>
Selected line will be substituted where
%a is in the first line.