Brusherator Preview is a simple satellite panel, that shows a large stroke or custom preview when you hover over the button in Brusherator. This is useful when you have small text buttons as a reminder of how the brush acts or to describe how a script/action button works.
Default preview size is 300x120px, to change it
Right-Click anywhere on the panel and use
Set Default Preview Size option.
To recreate a preview in case you changed the default size or a button, use
Recreate Preview from
Right-Click menu on Brusherator.