How to change keybinding?

[iwsnj]

Hello,
I'm a new user. I'd like to change a key binding, but it is not working for me. This is what I have in the preference right-side pane.

behavior {
theme "Kon"
}

keyBindings {
"Cmd+E" "core.go.up"
}

Is there some step I need to do to activate it? I tried quitting the application and restarting it. But there is no visible change.
Thank you,
Ivan

[iwsnj]

It seems like the file org.yanex.marta/conf.marco is not being processed. Even when I change the theme, it doesn't save it when I next open Marta..