Sandbox mode hasn't been removed - the interface has been updated. Instead of the "Live" button, you now access sandbox mode through the Actions menu. [1]
To enable sandbox mode:
1.
Click Actions → Turn on sandbox mode
Note: Sandbox mode requires a Pro or Enterprise plan. [2] If you don't see this option in your Actions menu, check your current plan level.
If you still need help with accessing sandbox mode or have any other questions, I’m here to assist. Would you like to provide more details about what you’re trying to resolve or understand?