When I’m trying to add a page to the reading list from other apps(like Twitter), There is no action for that, only one for Safari. I hope you can add one. Now I need to open the page in Orion and then adding to the reading list. When I want to add a link to read later, I don’t want to leave the current app.
Open the share sheet from other apps(like Twitter), then tap on “Add to reading list”. That's it! I do this a lot with Safari.