I recall seeing once, that someone had planted eight
apple trees in a circle and as they grew, trained the branches to connect and form a shady roof. In the end it created a sort of gazebo type structure which could be used for a variety of purposes. I suppose hammocks could even be strung up between the trees, or frames for the hammocks could be constructed so they could easily be moved.
It does require pruning, which I understand you avoid, and it would be permanent-ish. But that's the first thing that popped into my head when I read your post.
“The best things in life are nearest: Breath in your nostrils, light in your eyes, flowers at your feet, duties at your hand, the path of right just before you. Then do not grasp at the stars, but do life’s plain, common work as it comes, certain that daily duties and daily bread are the sweetest things in life.” Robert Louis Stevenson