Actually, it’s more of a keyboard longcut, using the well-known trick of Alt plus a 4-number sequence to enter a specific character. Just hold down the Alt key and type 0149 to add the bullet symbol. To enter multiple bulleted items in a single cell, use Alt-Enter to create a line break in the cell. You don’t get anything like the range of formatting options available in Word, but for simple bulleted items, it’s a definite time-saver.
Learn 3 time-saving Excel keyboard shortcuts [Inside Office Online blog]