Thank you! Found it! The top of the chart fits up under the tabs bar, obscuring the window controls for the chart when a chart is maximized.
It might be more apparent if something could be put on each tab or on the tab bar itself. But it is a minor thing-- once you know how it works it doesn't make any difference.
BTW, having mulitple charts on separate tabs is a nice feature. You recently added bringing up a chart from a watchlist and that also is very convenient.
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