Hello,
I am an independent consultant and welcome to Microsoft Q&A.
I'd be happy to help you further.
You can adjust it by going to the taskbar settings, then selecting Taskbar behavior, and scrolling down to Show Smaller Taskbar button. You can choose Always, When taskbar is full, or Never.
You can also adjust it by changing the scale or the Display Resolution of your computer. But this will change everything in your system.