Bayle Shanks's website: notes-computer-applications-gimp

How to get and use the path-arrow-heads plugin (i didnt write it, i just use it):

To install, chmod a+x then put it in a directory like ~/.gimp-2.8/plug-ins/ (with your most recent gimp version instead of 2.8). Now restart Gimp.

To use:

Open the Path dialog by using menu Windows->Dockable Dialogs->Paths.

First you need to make a path for the arrow. One way is to make a path with the Paths tool, but this provides no way to snap-to-angle in order to have exactly horizontal or exactly vertical lines. So, i prefer to:

use the freehand select tool to draw a line; first click on the starting point, then hold down Ctrl and Shift to make a straight line with snap-to-angle, and while doing this click the ending point
open lines can't be selections, so draw two more lines to make a triangle (the last line should end at the starting point) (we're going to delete these other 2 lines in a minute so don't worry about them for now); now we have a triangular selection
in the Paths dialog, at the bottom there's an icon with a small red circle; hovering over this will show you that it is for 'Selection to path'; click that to turn the triangular selection into a triangular path; this creates a new Path row in the Paths dialog
kill the selection by using a selection tool and clicking somewhere else on the image
double-click on the picture in the path row in the Paths dialog; this selects the path
delete both extra lines that we made to make the triangle, by holding down both Ctrl and Shift and clicking on each of them
delete the extra node that was in between the lines we just deleted by holding down both Ctrl and Shift and clicking on it
now we have a straight line path

Now to make the arrowheads, in the Paths Dialog, right click on the path you want to add arrows to and in the menu that pops up use the item 'Decorate->Arrow Heads...'. This creates another path with the arrow head.

There is probably some way to combine these two paths into one but i don't know how yet.

But to make an arrow, just select each path in turn and click the Stroke Path button in the Path tool area in the Toolbox. This draws something along the path.