Cell > Cell Properties > Active (Mathematica Menu Item)

Active toggles a cell between active and inactive states.

Insert > Table/Matrix > Add Column (Mathematica Menu Item)

Add Column adds a column at the cursor's insertion point in a table or matrix.

Insert > Table/Matrix > Add Row (Mathematica Menu Item)

Add Row adds a row at the cursor's insertion point in a table or matrix.

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

Close All Subgroups closes all groups in a selection.

[Right-click] > Copy Address (Mathematica Menu Item)

Copy Address copies the address of the selected (or clicked upon) hyperlink to the clipboard.

[Right-click] > Copy Hyperlink (Mathematica Menu Item)

Copy Hyperlink copies the selected (or clicked upon) hyperlink text to the clipboard.

Cell > Cell Properties > Editable (Mathematica Menu Item)

Editable toggles whether a cell can be edited or not.

Cell > Cell Properties > Evaluatable (Mathematica Menu Item)

Evaluatable toggles a cell between evaluatable and unevaluatable. Only evaluatable cells can be sent to the kernel.

Cell > Cell Tags > Find Cell Tag (Mathematica Menu Item)

Find Cell Tag opens a submenu to find and select cells based on their cell tags.

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

Generate Palette from Selection converts a selection into a palette.