KICAD PCB coil design related
You can use the Python console like this:

import pcbnew
from pcbnew import wxPointMM
board = pcbnew.GetBoard()
tracks = board.GetTracks()
new_track = pcbnew.TRACK(board)
new_track.SetStart(wxPointMM(STARTX,STARTY))
new_track.SetEnd(wxPointMM(ENDX,ENDY))
tracks.Append(new_track)


Alternatively, you can click on a track in pcbnew and type 'E' (or right-click and select Properties)


This will bring up the Track and Via Properties window where you can choose the start/end positions to finer than the user grid.