According to the Upverter Schematic Style Guide , we recommend marking floating pins using a No-Connect (NC) flag. This makes it clear that you've intentionally left the pin unconnected.
Simply hit the 'X' key then click on the component's pin to add a No-Connect.
To delete an NC flag, use the Select tool to do a box-select of the flag, then hit the Delete key. If the NC flag is directly on top of a pin, clicking it directly will start the Net tool which is why it's better to select the flag using a box-select.