Now, if you really want to delete the extra content after a crop, you can always go to Layers > Rasterize and trim…fdelaneau, Affinity Forum
This is exactly what I was looking for in Affinity Photo. Thank you! Most of the time I crop images and then copy them into a new file. But since Affinity Photo’s Crop Tool crops images non-destructively, copying a cropped image into a new file just brings all of the non-cropped extra content with it. Totally useless for my needs.
Thanks for the tip to Crop then go to Layer > Rasterize & Trim. Now I can successfully copy the cropped image into a new file.