victor99 wrote:
OK, but what can you do with it? When this happened, there was no undo. I would have been happy to just delete it. How would I do that? I had no idea it was possible to create a new sheet by dragging. Maybe if I read up on how that is supposed to work.
I had no idea either when I first observed the behavior. There is no substitute for just trying different things to understand what is going on.
I suggest you select a row or rows in a test table and drag them onto the canvas. You'll probably end up with a separate table. (In Numbers, these are called tables, not sheets; sheets are the "tabs" which contain a canvas on which you place tables, charts and other objects.)
Now select the cells in that new table and try dragging them back into the original table. If you do it right they should pop right back into place.
Selecting and dragging moves cells. Selecting and option-dragging copies them.
To delete an unwanted table, click in it, then click the concentric circles "bulls-eye" icon to its upper left and hit the delete key.
If you are new to Numbers be sure to have a look at the User Guide at Help > Numbers Help in your menu.
SG