What is the tag of progress on heart rate?

The tags are different for WFS than GWS but the concept is the same see Example of Heartrate Monitor for logical operations.

See this thread : How the tap action works (one-tap heart rate)
It is possible to check whether the “Measure heartrate” tap action works as well with other Tag expressions.
With [HR_IS_MEASURING] tag, you can notice that the heartrate is measuring by the action or not. Try it on opacity or rotation property for any visual component such as Image or Text. The property of the component will be updated while the HR sensor is working.
Also you can see the result of the measuring action through a Text component with [HR] tag.
※Note: the HR sensor works only while the device is wearing on the wrist.

There is no way to do a continual heart rate monitor that I can find at this time.

Ron
Samsung Developer Relations