Sets or updates custom buttons in the Daily Prebuilt tray.
updateCustomTrayButtons(customTrayButtons) Prebuilt CustomSets the custom tray buttons for a Daily Prebuilt call. Equivalent to setting customTrayButtons at call creation, but can be called at any time to add, update, or remove buttons.
The provided object completely replaces the previous set of buttons. To add a button to an existing set, include all current buttons alongside the new one.