Help getting started with Roku devices, including setup, connecting your device to your TV, linking a Roku device to your account at my.roku.com/link, adding channels, subscribing to services, and more.
As you've found, there is no way to maintain your channel lists on the web site, nor to modify the way the channels appear on a Roku device. The channel layout is controlled at the app, and does not transfer to other Roku devices. I agree it would be something nice to have.
Dan Roku Stick (3600), Ultra (4640), Ultra (4670), Premiere (3920), Insignia 720p Roku TV, Sharp 4K Roku TV, Nvidia Shield, Windows 10 Pro x64 running Serviio and Plex on a wired Gigabit network.