From Synfig Studio :: Documentation
- Eraser check box. When checked, the brush act has a rubber.
- Display the set of configured brushes (MyPaint brushes format). By default, synfig is installed with a selected set of brushes from "Concept Design (C_D)" pack by Ramon Miranda.
From the Preferences Dialog, you can configure the "Brush Presets Path" to use other brushes package (for example the ones listed by MyPaint)