Cell > Grouping > Close All Subgroups (Mathematica Menu Item)

Close All Subgroups closes all groups in a selection.

Evaluation > Debugger (Mathematica Menu Item)

Debugger opens the control palette for the debugger.

Cell > Delete All Output (Mathematica Menu Item)

Delete All Output deletes all output cells in the current notebook.

Format > Word Wrapping > Don't Word Wrap (Mathematica Menu Item)

Don't Word Wrap turns word wrapping off.

Cell > Cell Properties > Editable (Mathematica Menu Item)

Editable toggles whether a cell can be edited or not.

Insert > File... (Mathematica Menu Item)

File inserts the contents of a file at the insertion point.

Window > Magnification (Mathematica Menu Item)

Magnification changes the display magnification for a notebook.

Insert > Table/Matrix > Make Spanning (Mathematica Menu Item)

Make Spanning combines the selected entries from a formatted grid into a single spanning entry.

Cell > Merge Cells (Mathematica Menu Item)

Merge Cells combines selected cells into one cell.

[Right-click] > Open in New Window (Mathematica Menu Item)

Open in New Window opens the selected (or clicked upon) documentation link in a new help viewer window.