Sorry for being late :-D
Well, that exactly is my (only) workflow. I save my images to my NAS, import them into Lightroom. For some special actions I use Affinity Photo (mostly the repair tool), save the image an proceed developing the photograph in LR.
When LR is opened an I want to edit the image in AP, LR says "image could be blabla", but it is working well. If I leave AP open and try to edit the next image loaded in LR by loading it into AP, the system crashes.
Well... I hope for a Serif solution to kick LR :-D