To switch from one display to another, place your wrist in front of you as if you were watching the time, and made a frank wrist rotation. Each rotation changes the display.
You can also tap on the screen of the iHealth Edge.
*credit to Sylvain of iHealth Labs EU
https://helpcenter.ihealthlabs.eu/hc/en-gb/articles/210711769-iHealth-Edge-AM3S-How-to-switch-from-one-display-to-another