Variable: tabulated-list-sort-key

Sort key for the current Tabulated List mode buffer.
If nil, no additional sorting is performed.
Otherwise, this should be a cons cell (NAME . FLIP).
NAME is a string matching one of the column names in
`tabulated-list-format' (the corresponding SORT entry in
`tabulated-list-format' then specifies how to sort). FLIP, if
non-nil, means to invert the resulting sort.