As long as the glue is non-toxic I don't see why it would be a problem. But you wouldn't be able to remove it to clean it or fix it or anything if needed. I feel that using wire or maybe even velcro to secure it would be better as it makes it possible to move it around if need be. I'm new to chameleon keeping (2 months) maybe someone who is an expert will chime in with some non-toxic ideas.
I would not glue it in , it rips up the screen when you try to take it out- you can hot glue a big paper clip on the back, so it looks like an S - then bend one end so it sticks threw the screen - the crix will shed/poop in it - you will need to clean it - just sayin