I have a lot of boxed items in the game, but I can't preview the items in the shulker box in the wireless terminal. How can I operate it to see the items in the box without taking out the shulker box

What mod are you using to preview? The terminal uses fake slots, so some mods may not detect it.

That doesn't sound like functionality this mod would provide. The network requires physical connection to the inventories being used, and you can't get that with a shulker in your inventory.