Edit - Redo

Ribbon bar. On the Quick Access toolbar, click ...

Classic menus. From the Edit menu, select Redo (or click the toolbar button)...

...to counteract an Undo action. For example, if your last undo action command was to undo bold formatting to the selected text, then select Redo to reapply bold formatting to the text.

Note: On the classic menus, the name of the option changes depending on which action you have performed.