I'm not a UX designer, so I'll leave the logistics to Affinity to figure out. I come from InDesign so having this function makes perfect sense to me - Hide Frame Edges or Boxes - YouTube. I only need to see a Frame Edge or Bounding Box when I click on single element or multiple elements using Shift, otherwise complex layouts with multiple assets look incredibly messy with dozens of boxes. Not to mention overly confusing. I only need to see a Frame Edge or Bounding Box when I click on an element and that's it. Otherwise it's just visual clutter, to me anyway.
What is the benefit to having Frame Edges or Bounding Boxes active all the time? I don't see one. It's a needless mess.