Hello!
I’m a beginner to 3ds max and I’m trying to model a chair or part of a chair as seen below (the grey model is an .IGES file I use as a blueprint). The problem I’m encountering is that whenever I add the cut-outs to the geometry, 3ds Max connects them to the outer edges. I guess this is because otherwise they’d be floating in space but the problem comes when I try to chamfer the edges and this “extra” edge destroys the surface.
I really want to make this model with great detail and so I need to find a way around this problem. Any suggestions appreciated!

The extra edge:

And this is what it does to the surface

Cheers,
Binary12