Tapping the screen will pause the trend mode. Tapping again will make it play again. You’re not the only one who didn’t magically intuit this, I think the functionality should move to a labeled button (it already has on the Android app)
Scrolling live data is a little more complex because this involves adding another “mode”, which is that the view window is not attached to the end of the graph but the graph is not refreshing. Right now I’m inclined to leave it so you have to pause to scroll because I can’t think of an elegant way through the details of that interaction. But I’m inclined to switch graphing libraries entirely soon because directional zooming is not well supported right now. Let me know if you have a specific graphing library to recommend or an example of what the interaction should look like.