The scenario is this: I have a folder with full-size landscape and portrait images I want to resize to max of, say, 800 width or 800 height for portrait). In addition, after the resize, I'll want to run additional sharpening. I've usually done this with a batch script in PS but the batch capability in affinity appears to preserve both dimensions recorded instead of applying only the value I changed. For example, I record a macro: change x dim=800 (affinity changes y dim to 640), sharpen. When I apply the macro to an image with slightly different proportions, it resizes it to the same 800x640 instead of fixing 800 and recalculating 640 for the new image proportion.
I guess what I'm really looking for is resize using constraints. An 800x800 constraint would limit the long side to 800 and recompute the shorter side accordingly.