Changing the symbol
Click on the 'Symbol' column and type the new symbol.
Changing the shares or weight
Click on the corresponding column.
Removing a position
Click on the thrash icon at the end of the position line, as shown circled in red in this example:
To delete a position is to liquidate it: its value is transferred to the $CASH position.
If you wish to remove the position but not transfer its value to $CASH, set the number of shares to 0 prior to removal.