Resolved! Accessing the last element of List of List x:(`Col1;12;.z.Z) y:(x;x;x) //add gtime of last element to end of x x,@[gtime;last x;0Np] //How do i do this for y? So i think i did x correctly unless theres a better way. But how would i handle y? I want to append to end of each list in y.