When multiple charts are added to a Service Analytics dashboard, there is a gray line that appears to the right of the row of charts when you hover just to the right edge (or in between 2 side-by-side charts) that can be dragged to make the charts either wider or narrower. However, there is no gray line that appears when you hover in between charts that are on top of another to make the charts taller or shorter. This has been duplicated locally (by me) in version 20.19.01 in all supported browsers (Chrome, IE, FF, Edge).
There should be horizontal line to adjust the chart like we have vertical line.
1) Access Service Analytics and create either separate reports or enough charts so that at least 2 can appear on a Dashboard
2) Create a new Dashboard
a) When the dashboard screen appears, press the "+ Add" buttons to add the charts to the dashboard.
b) Press "Show Dashboard" in lower right of the dashboard panel.
c) Save dashboard with a name but you can also just proceed to Step 3.
3) When the charts appear, point to the right edge of the charts so a vertical grey line appears as in the attached screenshot. This line can be dragged left or right to widen or make the charts more narrow.
a) Hover the pointer in the space below a chart that has another chart underneath it.