Network files open if you opened them first in Arduino 1.n. There's some re-open cache, where the app re-loads the file that was open at last exit.
2.0 uses the same cache, so if the cached file is a network file it opens it. So the issue isn't that it can't do it.
But weirdly it doesn't always work - I went back and opened a different network file in 1.8 and then closed and opened 2.0 and it still loaded the previous file, not the most recent one.
@ptillisch lookslike you are already working on this - thank you very much.