So I’m new to this and enjoying starting out on the training programmes.
The one I’m doing asks for a certain watt / cadence combination for a particular duration.
On the screen it shows “spin faster / spin slower” and/or “more power / less power”, which is helpful to try to get you into the right speed.
As a beginner It took me a bit of time to figure the right gear to be in. Given that with a fixed resistance, in a particular gear cadence and speed (power) are directly related, it should be possible to also say “gear up? gear down?”.
In fact a test of going through the gears at a particular cadence probably would give zwift enough info to tell you what gear you ought to be in…