The following steps explain how to enable the minimize and maximize buttons for a grid or graph on a dashboard in Strategy Web 10.x:
1. Right click on the grid or graph object in the dashboard template and click on Properties.
2. Under Portal Window section on the General tab, select the option to Show Title Bar.

3. Hit Apply and then Ok.
4. The minimize and maximize buttons should now be present:

Note: Maximize and Minimize buttons are present on the grid/graph title bar. Disabling the title bar will also disable the maximize/minimize buttons. Currently, there is no way to have maximize and minimize buttons available without enabling the grid title bar.