In Chrome, the scrollbar on the scheduler is very thin. Is there a way to the size of the scrollbar?
The Scheduler theme doesn't define the scrollbar appearance. It will use the default styles (defined by the browser or by your global styles).
If you want to modify the default scrollbar appearance, you can do it using ::-webkit-scrollbar pseudoelement (applies to WebKit-based browsers, i.e. Chrome, Safari, latest Edge) on the .scheduler_default_scrollable element:
/* ... */