You can save your favourite pens, highlighters and erasers in Notability.
- When you have chosen your pen/highlighter/eraser, tap on the Favourites icon at the bottom of your popup window to add it to your favourites.

Tips:
- Tap the bar on the beginning end of the favourites toolbar to move it around the page.
- Tap the X icon to tuck it away.
- Tap the star icon (bottom left corner) to bring it up.