Click the 3 dots next to any of the grid headers.

A list of options will appear. Navigating to "Columns," it will show you all the category options for potential columns. Clicking the checkbox will make that column appear in the grid.

Drag a column header and drop it here to group by that column

Unselecting the checkbox will allow the column to disappear from the grid.

You can see here how the column has vanished. You can use these options to make your grid as wide or as narrow as needed for your purposes.

Grid Columns