Delete on the canvas asks nothing; undo restores what it took
A delete on the BaseHalf canvas happens at once and asks nothing. One undo puts back the files as they were, with their places, descriptions, and connections. Deleted items go to the Trash when the window closes.
On the canvas, a delete happens at once. There is no confirmation. The card is gone from the view.
The safety net is undo. One undo puts back exactly what the step took.
What a canvas delete takes
A delete on the canvas asks nothing. What you deleted goes to the Trash when the window closes.
One undo restores those files as they were, with their places, descriptions, and connections, whatever their size. You do not have to recreate the card, redraw the lines, or type the description again.
If you selected two or more cards, they are a set. The set toolbar includes Delete. That delete is the same kind of step: it asks nothing, and one undo brings the whole set back.
Why the canvas does not ask
The canvas can skip the confirm step because undo is complete. It does not put back a bare file and leave you to restore the layout by hand. Places, descriptions, and connections return with the files.
Size does not change the rule. A large file and a short note are restored the same way: one undo, the step in reverse.
The sidebar still asks
A delete in the sidebar's file list still asks first. If you want a chance to cancel before anything is removed, delete from that list.
The two places serve different moments. The canvas is for cards you can see, where undo is close at hand. The sidebar is the file list, and it keeps the confirm step.
The canvas and cards docs spell out both behaviors under deleting and undo. Delete on the canvas is immediate. Undo is how you take it back.