What is the method to collapse or expand rows & columns in an Excel sheet?

Answer 1

You can use group/ungroup to expend or contract rows or columns entries. It is in the DATA on the ribbon. Highlight the series of cells then click group. It will add a area to the left of row headings if you are grouping rows or above column headings if you are grouping columns. If you click the minus it collapses the group, if you click plus it expands the group.

Answer 2

The data must be grouped. Then click on the + to expand a group or once expanded, click on - to collapse the group.