Hi!
The "Resize Pixel Art Document" feature is completely broken, at least for me. When using this feature, the final result is always a blank transparent file. I've attached a video demonstrating what happens when I use it. The image in the video has transparency, but the result is the same when using non-transparent images.
I hope this can be fixed soon... Unless there is some preparation I need to perform on the image before using this feature that I am unaware of... The official Affinity Photo documentation doesn't mention anything in particular.
2019-10-24_09-57-53_T.mp4