It would be cool if a canvas inside another canvas simply looked the same as a “Group” inside a canvas. In other words, it’s rendering all the objects as if it were part of the same canvas, but has a border around it like a group.
Work-around could be a script when opening a canvas to temporarily swap out the embedded canvas
{“id”:“8afb3ddca6ce3040”,“x”:-583,“y”:-902,“width”:831,“height”:503,“type”:“file”,“file”:“My board.canvas”}
with the coordinate/scale adjusted items from the other canvas file, wrapped in a “group” box. Then swap them back when you “save”. Or if it’s a read-only view that’s much easier to just run a one-way copy