Format > Edit Stylesheet... (Mathematica Menu Item)

Edit Stylesheet edits the style definitions for the current notebook.

Palettes > Generate Notebook from ... (Mathematica Menu Item)

Generate Notebook from Palette converts a palette into an ordinary notebook.

File > New > Notebook (Mathematica Menu Item)

Notebook creates a new notebook.

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

Open All Subgroups opens all groups in a selection.

Help > Register this Mathematica... (Mathematica Menu Item)

Online Registration opens the Mathematica registration website.

Cell > Cell Tags > Show Cell Tags (Mathematica Menu Item)

Show Cell Tags toggles the display of cell tags in a notebook.

[Right-click] > Speak Selection (Mathematica Menu Item)

Speak Selection speaks the contents of a single selected cell.

Step Out stops the debugger after finishing all evaluations in a stack.

Evaluation > Debugger Controls > ... (Mathematica Menu Item)

Toggle Breakpoint toggles a breakpoint on or off.

math (Mathematica System Program)

math options starts the Mathematica kernel in Unix and Linux.