I'd like to insert perfect arrows (the sort you can make using Inkscape: straight, symmetric tips, of customizable width and length, *etc.*) into images in GIMP. At the moment the closest thing to this I can do is by holding down "shift" whilst using the PaintBrush tool which just creates straight lines (with no arrowheads).
This is a great option. You can also use any number of assets found online for free and editing them into your image. Search for something line "Vector arrow line free" and see what is available.