Add an elbow pointing downwards that is the same size fitting as the black flex line. You can then rebend the flex line so it is completely hidden under the glass. All you will see is the current fitting and the elbow.

It would be even cleaner if you can replace the fitting that is coming into the fireplace with an elbow, but you may not be able to get a second wrench on it to hold the incoming pipe so it does not unscrew. You can try taking that fitting off anyways and if it seems to come loose without the inner pipe unscrewing, you can do it yourself. Otherwise, you will need a plumber to do it so you don't end up with that inner pipe leaking.