How do you repair a stained glass crack with crazy glue?

It does require some skills to repair a cracked piece of glass in a window, no matter what method you choose. Is it a single crack? Multiple crack? Is the cracked piece in the border or within the main body of the window? If it's in the border area, then it may be easy for you to remove the piece and either repair it or change it. If it's in the main body of the window, it gets tricky. My recommendation would be to bring it to a stained glass repair person. If you decide not to, and the window is not of any historical value then you could just infuse the crack with "Crazy Glue." Just clean the cracked piece with acetone using a cotton swab and make sure you flush the crack well with the acetone. Wait a minute or two, and gently apply the glue starting from the center of the crack and working your way to the edges.

Give it a try and if you are not happy with the result, the process is reversible.