Start a New Line in the Same Cell

Using the Start a New Line in the Same Cell Shortcut

Windows keyboard shortcut

 
Mac keyboard shortcut

This Excel shortcut enters line break inside the same cell. Ensure "Wrap Text", from the Alignment section, is activated to see the line wrap in the cell.

Normally, pressing Enter would move the cursor to the next cell. This shortcut moves the cursor to the next line within the same cell.
Other useful Cell Edit Mode keyboard shortcuts