The other mode is "content editing" mode, in which you can insert text or other elements (including other tables) inside table cells. In this mode, the gray handles and icons are not present.
To change from structure editing to content editing mode, double-click in a cell. The cell's contents are selected, and you can type or select an element from the toolbar to replace them. To change from content editing to structure editing mode, press Control and click in any cell other than the one that was selected.
Alternatively, you can switch from one mode to the other by clicking in the toolbar. Also, after you've clicked anywhere outside a table, clicking in the table puts you in content editing mode; Control-clicking puts you in structure editing mode.
In structure editing mode, you can:
A special case arises when you have embedded a table within a table cell. In this case:
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