Would be helpful indeed. A complementary command would be Image > Expand/Resize Canvas to Fit All Content, so canvas expands to contain all hidden pictures outside canvas. The latter would be more useful for artists who want to permanently work with the new items and export them, while editing content outside the canvas is great when you need to frame a scene but still draw context around it (or sometimes just drafts and researches - currently only References work out of the box outside the canvas, not own drafts).
EDIT: added feature proposal for this one: Add Image > Expand/Resize Canvas to Fit All Content
An alternative would be to allow export frames, in which case the artist would always work with a very big canvas, but select a smaller frame for export, which corresponds to what we currently use as canvas. From here we could expand the feature to multi-frames like Affinity products; but that would be for another proposal (which I don’t find btw, if anybody knows a similar proposal, please post the link to it).