A graphical user interface (GUI) for a messaging or chat application on a mobile electronic device launches, responsive to user-selection of a particular message cell in the GUI, a contextual message overlaid on an underlying scrollable message board or list. The action menu comprises a preview area displaying a preview of message content of the selected message cell, and further comprises one or more user-selectable action items for executing respective corresponding user actions with respect to the selected message. The preview area is automatically scaled and positioned dependent on one or more attributes of the selected message cell.