I am not familiar with the Flex Grid. I have 6 charts in a grid. While in the grid, if you hit the drop down, click Maximize Cell, It will lay the charts on top of one another and put 2 arrows next to the grid symbol in the top right of the chart. You can toggle between all 6 charts and each chart is full size. Each chart can be a separate time frame, separate indicators, etx. 

I know what it is, but I have not used it. I do have multiple charts and multiple windows.