There are 3 layouts for choosing: AutoSize, SizeToFit and Fixed. And also you can customize the max width of Tabs (for AutoSize and SizeToFit layout), and fixed width of Tabs (for fixed layout). Sometimes we need to deal with many documents with a long name. If tabs display its whole name, the tab bar will be crowded. In this case, setting up a max width of the tabs will be better. Go to the setting center, choose the "Style & Color" tab, and then choose the layout as the following picture shows: