@totalsonic Thanks. That is indeed the solution.
Open the terminal app and type:
$ cp /userdata/user-data/phablet/.local/share/uwp.costales/file.html /home/phablet/Downloads/file.html
Then open the file by typing the new address of the file in the address bar of the Morph browser:
file:///home/phablet/Downloads/file.html
That's it.