Very good question! There are a few ways of doing that, but IMO the easiest way is to use patching rather than edit forms. This way you can place the controls on several screens any way you want, and then patch them all in one submit action. Learn more about patching here:
https://powerapps.microsoft.com/en-us/tutorials/function-patch/ Head ups! When patching to SharePoint Lists always include the Title field in the patch, even if it is hidden.
