This is not the philosophy behind Wear OS Powered by Samsung (aka Wear OS 3) nor Watch Face Studio. See the**documentation on Complications**
The philosophy for WFS is to have a tool that designers can use to create Personalized Watch Faces with a standard user interface that is compatible with all Wear OS 3 devices.
As for barometric pressure and other sensor information. WFS may be able to access and create tags based on sensors. I can add Tags for Barometric pressure as a request but if they are not supported on all WearOS 3 devices that may not be possible. Also something as simple as the current barometric pressure data may be considered a privacy issue and that adds another factor.
There are Android Studio tools that you may consider if you wish to access and develop watch face apps for Wear OS other than Watch Face Studio.
Ron
Samsung Developer Relations