@garrett@notting@adamw Right, I can figure this out on a case by case basis. But it's not something that's reasonable to ask of all users generally. If part of the flatpak spec was where the configuration lives outside flatpak, then flatpak itself could offer to move (or copy) configuration when installing a flatpak for which existing "legacy" configuration existed.
It's somewhat analogous from an end user experience point of view to how browsers offer to import your data from other browsers. But done instead across locations for the same app, and configured declaratively so that it's implemented once in flatpak itself. The app itself literally can't do that because the whole point of the restriction is the additional sandboxing, as I understand it...