The Web IDE was not designed keeping iPhones in mind. But I can see how it might be useful in certain situations. I’ll raise this topic with the IDE team. It may not be a high priority for us though.
Although (far) from ideal, you can in fact scroll the window on iPhone/iPad by scrolling on the far edges of the screen (the right, or bottom edge). It will be impractical, highly frustrating, but in case of “emergency” it’ll work. Just don’t expect to write a 800 line sketch off your iPhone without throwing it at a wall a couple of times
Best of luck, and may the s be ever in your favor.