The “Insert attachment” command is currently only available for notes, but not for canvases. Some graphics may only make sense on a canvas and not for a single note.
Just implement it the same way it works for notes. It’s just importing the file to the configured location and using its path in the canvas JSON, if I didn’t miss anything.
- Insert attachment to a note in the desired location (next to the canvas)
- Remove the link to it from that note
- Use “Add media from vault” feature to add that note to a canvas