It would be handy if you could COPY in other programs like Aseprite, Photoshop, Affinity designer [copies as SVG]...etc and PASTE into Pixel over as a new object layer

Hey, yes clearly, I will make that for a future update.

Implemented in 0.8.2, should work with Aseprite and photoshop but I don't think so for affinity svg (doesn't work with inkscape)