The level format of Lemmings 2 is rather different, you just have a matrix that stores for each field in the map which terrain tile is in it. Objects in the levels are handled similar to Lemmings 3, but the object definitions are plain horrible as they are set up of components with a bunch of special exceptions.
Essentially I have all the routines done that extract the graphics and level data from the files and bring them on the screen, only thing I'm yet to do is the user input and writing to files.
I've used OpenGLUT for writing it, so it should be platform compatible, and I'll release the source anyway once I'm done. But the code is a mess, for the reason that I'm a sucky programmer, and the fact that GLUT is C-based and thus doesn't allow for proper object oriented programming.
So if I really put some effort into it, I could get it done still today. No promises though.
I'm not sure about the Amiga editor, but I suspect that its functionality will be way beyond my editor, so I guess it might still be worth a try to get it to work.