check out this small marker-editor i wrote
http://mnml.is/landmarked
drop a .stl file on the canvas
rotate: rmb
zoom: wheel
set marker: lmb
save markers: [ S ] (can only be saved when all markers are set)
clear markers: [ C ]
load markers: drop .pts file on the canvas
in case you need test data (stl & pts):
http://mnml.is/landmarked/testdata.zip