Ideas for keeping Mom's call lite cord in her tray?

Does she even know what it's for?

Clip it with a huge clip. What makes you think she knows what a call light is for when she has dementia?

I am a special education teacher and Velcro is a lifesaver! It's amazing the number of things you can Velcro to other things....

I was going to suggest Velcro also. I even use it under my husbands CPAP machine and his electric blanket control. He also has dementia and tends to bump things around a bit.

I bought a box of VELCRO - Industrial Strength - Extreme - 4" x 1" Strips
They are easy to use. They are designed for use with objects not fabric

Velcro. Put a strip on the back of the call light and a strip on the tray.