I've been trying to do the very same thing and found that when using the stringify method on the graphics the type was being lost so I had to recreate a new object and save that out so that it would then be able to be drawn again later.
I could well be missing some simple OOB method, so maybe someone else will have a better answer but this works for me:
const result = [];
this.graphicsLayer.graphics.forEach((item) => {
// for some reason the stringify method on the graphic drops off the type of geometry (polygon, polyline etc.)
// from the object so when we try to use the saved value to draw it, it fails as the type isn't there.
// so here we take the geometry of the item and them parse it into a new object, add the missing property
// and pass that to the stringify method so that we have all of the expected properties at the other end.
var geometry = JSON.parse(JSON.stringify(item.geometry));
geometry.type = item.geometry.type;
// add the newly constructed geometry to the result
result.push(JSON.stringify(geometry));
});
return JSON.stringify(result);
This only applies to the geometry as that was all I was interested in keeping but similar should work if you need the other propeties.
Cheers
