Row/Col resize handles appear when the cursor is placed over a row/col border line in the rol/col title area.
A popup menu for row/col insert/delete appears when the mouse is right-clicked in the row/col title areas.
Cells activate (i.e. the contents become edit-able) only when the cell is double-clicked or the F2 button is pressed. The default Tk::TableMatrix behavior is for the cell to be activated when the cell is single-clicked.
The Escape key causes any changes made to a cell to be canceled and the current selection cleared.
The return key causes the the current cell to move down.
The tab (or shift tab) key causes the current cell to be moved to the right (left).
The delete key will delete the current selection, if no cell is currently active.
The Mouse button 2 (middle button) paste from the PRIMARY. (Control-v pastes from the clipboard).