Area charts are now a line chart setting
The Area chart type is gone — because it never was a separate kind of chart, just a line with the space underneath filled in. That fill is now a setting on line charts: Fill under line, in the Style tab.
One type, one slider
Build a line chart as usual, then open the Style tab and raise Fill under line. At 0 % it is a plain line; around 20–40 % you get the classic area look; at 100 % the fill is solid. Every other line setting — shape, dash, dots, colors per series — applies as before, so you no longer have to choose between "line" and "area" up front and lose settings when you switch.
Series split by Color by each fill down to the axis and overlap, the same way they were drawn before; only the axis now sizes itself to the tallest series rather than to a stack that was never drawn.
Axi knows the change too: ask it to fill the area under this line and it sets the opacity for you.
📖 Charts