You may want to delete freehand lines and shapes in a plan view drawing. You can use the eraser to delete them.
To use the eraser, click the "Eraser" icon on the toolbar, then click the freehand line or shape you want to delete.
The eraser deletes only freehand drawings.
To delete an object, such as text, shapes, and comments, use the "Delete" icon in its contextual menu, or select the object and press "Delete" on the keyboard.
To delete multiple objects, select the objects and press "Delete" on the keyboard.
Check out this article for more details.