This conversation seems to have ceased but I continue to have troubles of my own with this issue. In the preceding page design apps that I used for this kind of work (Indesign, Quark, PageMaker), I could rescale a placed graphic by holding down the shift key and dragging a corner. When I attempt this in Affinity, the proportions of the item are not locked, so that it becomes distorted while attempting to rescale.
Looking for help in your documentation I could only find https://affinity.help/photo/en-US.lproj/index.html?page=pages/SizeTransform/imageSize.html?title=Changing image size
That document is inappropriate for my need, which is a simple constrained scale as described above. How can I simply place and scale a graphic element?