This is feature that is available starting in MATLAB R2018b. To enable scrolling on a Tab, you can set the 'Scrollable' property to be true.
The following example from the documentation illustrates what this looks like outside of App Designer on a UIFigure:
In App Designer, you can also set the Tab 'Scrollable' property to be true by selecting the 'Scrollable' property under 'Interactivity' in the 'Component Browser' when you have selected the Tab object.
For scrolling to be activated when the app is run, you need to place at least one component outside the borders of the Tab. Specifically, to activate up/down scrolling, place a Component onto the Tab and have it extend past the top of the Tab. To activate left/right scrolling, place a Component onto the Tab and have it extend past the right of the Tab.
To illustrate, refer to the attached example app. It was created in R2019a, but will also run in R2018b (though it may warn you that the app was created in a newer version).
