Thank you! For anyone coming along later, here's what I did:
- On the main menu, enable Developer Mode from Options.
- Load the character. It will say something about invalidating your save, but this didn't break anything for me.
- Press Ctrl-A to enter the Debug Menu.
- Transport to zone Unhallowed Morass (level 1 is fine).
- Save and exit to main menu.
- Disable Developer Mode.
- Reload the character and resume the Future Echoes quest.
After I did this, I was able to complete Future Echoes and get a new Temporal Warden quest.
Thanks again!