There doesn’t seem to be an Eraser option for the sketch tool either that or it wasn’t documented.
Other nice features
The option to make, straight,curvy or free hand for sketch tool and switch between them anything while drawing using shortcut keys.
Having a bline type way to make sketches for more precision.
On a side despite having a star tool there is no triangle tool.
Use the Star tool and select 3 points and check Make regular polygon.
How do I make the star into a regular polygon and is there an eraser tool.
If the Star layer already exists, just check the “Regular Polygon” checkbox at the end of the parameters panel of the selected star layer. It will turn into a regular polygon instead of a star. Modify the number of sides to convert it to a triangle.
And there is not an eraser for the Sketch layer and I don’t know if there will be any time.
There is an ‘undo last stroke’ button.
The idea with sketch is to lightly map out the scene. As it’s never going to be rendered, you can add more lines where you want them, and ignore the ones where you made a mistake.