I didn’t find any button or keyboard shortcut to go back to the main menu or quit the game midway through the Fort Freiheit mission.
Tried pressing the ‘esc’ button, but it doesn’t do anything. Alt+f4 did shutdown the game though.
There is no mention of this in the game guide pdf as well.
Maybe I’m missing something or this feature is not there I guess or it might even be a bug. Not sure.
Please forgive me if it is something obvious and I missed it
You haven’t missed anything. There isn’t currently an exit button within the missions. The technology just isn’t there yet.
There’s always the Exit Mission via Use of Explosives option. I’ve tried it and it works well 
Thanks for clarifying 
Sometimes one plays so bad that they would want to quit to escape further embarrassment. Alt+F4 it is till there is a better way i guess 
There is no quitting in Phoenix Point!
As mentioned on previous posts only way to exit is VIA explosives. Might be a full game feature! No quitting!
I dunno if you read the mission text.
You’ve been infected, you’ve been sent in to die for the greater good of humanity. There’s no turning back. Kill or be killed.
On a more serious note, I had the exact same thought. I couldn’t find the menu button either, and it would be nice with at least some “Surrender to Alien Overlords” aka “quit” button
Oh man! no quitting. Good thing I got the backer build. I’ll hone my skills by the time the final game is released.
While full blown menu is too early for single maps we play today,
if some save/load can be introduced for time being - it would be helpful.
and at least exit game (by not pressing ALT+F4 on WinBlows)
There is already an exit game option in the menu.
I ment within the game. So for example, I could save position, exit, continue tommorow 
Missions are not long, turn based games can be “paused” by simply walking off, but yet, such feat if not complex would be expected.
If not for playability duration (games are not long now) then for example for showing tactics and situations or revisiting them.
I understand what you’re saying. While there isn’t currently a save option, there is still an exit (plus return to main menu and restart map) option in the menu in-game. Just click on the gear in the upper right corner.