Currently, the only way to reorder fields in a form is to drag them up or down. While this is somewhat intuitive and seems like a good idea, it's a huge pain when reordering many fields. Also, it's sometimes unreliable. For example, sometime when you drag a field up or down, then when you move another field, the first one snaps back to its previous position. I've experienced this behavior in Edge (when it decides to not crash on me - another gripe for another time) and Chrome (which seems to be what the vast majority of folks - even Microsoft MVPs and employees - use for PowerApps).
If you need some inspiration on what a "better means" might look like, this is what is available in the Blackboard Learn LMS. They call this the "keyboard accessible" reordering method. I call it the "elevator button", and it's a lifesaver when you want to move things up or down on a page, particularly when doing so would involve the page content scrolling. PLEASE, PLEASE, PLEASE put something like this in PowerApps. Heck, I'd even settle for something like the control for reordering columns in a modern list view. But the current mechanism is driving me insane.