The newest FTF build is now live. The most notable change addition is the ability to create a "private" multiplayer game. The functionality needs wider testing.
When selecting a multiplayer map you will see a new "private" toggle. Checking the box will change the buttons on the menu. Pressing "private game" will bring up a UI that will let you name your game.
To have your friends join your game simply give them the exact name of the game. Should be that simple. Love to hear feedback on this new feature.