When I think about the concept of expanding content, especially in regards to a data grid, I think of similar concepts to spreadsheets which usually just visually increase the size of the cell temporarily (or use a different part of the UI to show the whole thing but that's because their editable).

EuiDataGrid differs from this behavior where it shows the full content popover next to the cell. Historically I think this was the case because we utilized the same popover mechanism that is the pattern of a button triggering different content which then makes sense to keep the originating button in view.

However, for a data grid, or the concept of "revealing" content, this positioning mechanism doesn't fit expectation. Also considering a general use case for data grids is to compare cell values, covering other cell contents makes that harder.

This is especially true for more complex contents:

Existing:

Proposed:

This doesn't completely fix the "overlapping other cells" but it sure minimizes it even with simple content: