How to tile two sheets in a single floating container one above the other (The above completely covering the below sheet)?

Please consider the highlighted sheet in the dashboard. This sheet is opened and closed using show/hide button at the left side of the black box.

I want to make a rounded corner white background box for this sheet, which should show/hide through the same i-button, so that both the sheet and the rounded corner white background should show/hide simultaneously,

How can I do that?

I was trying to tile a blank white sheet (with area annotation as rounded corner) and the data sheet shown above in the same container, one above the other, the data sheet completely covering the background white sheet. But in the container it is placing side by side either vertically or horizontally.

Is there any way I can do this?

Note: Please find below the workbook, I removed all the background white box theme as I made it in Power Point, to make it accessible to the reader.