Hi,
Now that Microsoft Edge, Mozilla Firefox and Google Chrome are able to handle webp I find in incredible that it's still not implemented in Affinity Photo and Designer. Hoped that Affinity was a bit more upfront with the latest developments as they happen, but unfortunately this is not the case. Every day I'm converting images from TIFF or jpg to webp, but with an other application. The code for webp conversion is freely available on the Google website and easily implemented. Be smart