I share the same frustration about not being able to trace an image. I've been using Serif software for over a decade. Their much older vector-based software Drawplus X8 had a tracing feature called ImageTrace where you could convert a picture/ jpg into lots of tiny individual vector objects. You could trace any image into a black and white trace, a logo-like trace (with limited colour pallette) and a photo-like trace. After the image was traced, you could change the shape of each individual vector object using the node tool.
I've used, and loved, ALL of Serif's software but I can't, for the life of me, work out why they won't add a trace tool to Affinity Designer, especially when they had it in their older programs. Soooooo many people have asked for a trace feature. Pleeeeeease Affinity, please add this feature!