[dole]

Enter a N or n into the Editing box, you'll see the two grids that make the glyph up along with a blank third grid on the bottom, add a small tilde in the top two rows. Or copy and paste the actual Ñ or ñ characters into the Editing box to create it new, and you can use it immediately with the alphabet textbox on the left.

[cgriswald]

The editor doesn’t understand ñ and you can’t make a tilde because it requires a minimum of four points of width.

[mistercow]

Yes, and those glyphs don’t fit the grid. Try to redraw the n from the original font yourself. You can’t, because you can’t add points between the grid dots.