All modern ATs (including CVTs) have enough safety precautions built-in, that you can't wreck the transmission through the paddle shifters. For one, even if you hold the gear all the way to the redline, the car has a rev limiter that keeps you from going beyond the safe rev range. Some cars even go further by automatically shifting for you if you hit redline, even if you don't shift up via the paddles. You also won't be able to shift down if the lower gear would result in the engine revving all the way to the redline.

The basic pointer for a paddle-shifter-equipped car is to drive it like a manual. Usual shift point is 2000-3000 rpm, depending on the car and the load. On steep uphills, you can stay longer at lower gears (1st or 2nd) at higher revs (3000-5000 rpm) to generate enough torque to propel the car. On downhills, you can downshift to lower gears to increase the rpm and use engine braking to lessen the strain on your mechanical brakes, lowering the risk of brake fade.

Most modern ATs nowadays though are smart enough to know that you need more revs when going uphill, and thus stay at lower gears, even if you just keep it in D. This is especially true for CVTs like in your City, since it can adjust to any gear ratio to maximize the power/torque without sacrificing efficiency.