That looks like a perfect spot for elderberry to me. In Oregon, they tended to prefer a little shade, and they loved a moist spot.
You might find some more good ideas in Steven Sobkowiak's videos (Miracle Farms in Canada, a commercial
permaculture orchard), particularly this one where he talks about using plants for deer fencing.
I learn so many neat things from his videos. In an other video he talks about his favorite groundcover plants for his guilds. I was astonished to see that one of his favorites is also one of mine - Sylvetta, the
perennial arugula. I was surprised because he's in zone Freeze-Your-Butt off Canada, and I'm in zone 8a desert SW - sylvetta grows great in both places?! Wow. And on top of that, it grow both in out in the open, desert sun 115F, and also as an understory in a fruit orchard? (And his orchard understory is quite shaded.)
It's an amazing filler plant. In the desert here it is edible in two big bursts, well edible to me. It's always edible...but it gets extremely peppery as it starts to bloom (and too hot for me), and it blooms twice here. It has rhizomes; thick
roots weave around under it, and it can withstand significant drought or be sitting in a good amount of wet soil.
But back to his video here, he talks about building fencerows, essentially. And deer are a big problem for him, too.
And something maybe worth considering... It would take some management, but the food output is so good - an American, Chickasaw or Beach plum thicket. They can grow at edges and still fruit with a significant amount of shade.
Here is an article talking about growing American plums:
Akiva Silver, Twisted Tree Farm: Growing the American Plum
And this is what a basket of his American plums looks like!
Good luck and please keep us posted!