The simplest way to delete a symbol is to choose the eraser tool in the toolbar and click on the symbol (click on the upper left edge of the symbol.)
Another way to delete a symbol is as follows: Choose the arrow tool in the toolbar. Select the symbol to be deleted by double clicking on it. Select Cut from the Edit menu and the symbol will disappear. (You can paste the deleted symbol to a new location now if you wish.)
You can also select the symbol to be deleted by choosing the arrow tool, dragging a box around the symbol, selecting Cut from the Edit menu and then selecting an appropriate choice from the submenu.
You can delete a symbol entered from the keyboard by positioning the cursor over the symbol exactly where it was entered and then pressing the DELETE key and entering the same keyboard command used to enter the symbol.
Adjust notes within a beamed group