Hi everyone!
This thread is already quite old, but for everyone who is reading this in 2022, and asking themselves this question: They have already added this feature, although it's not really obvious.
You can open external apps by clicking on the shield icon, and choosing the option "Open im external app". This works only on certain websites, though, such as YouTube.
Of course, it's still pretty inconvenient because it doesn't work with the majority of the apps, but who knows, maybe they will add more apps soon?
