Description
Due to a incompatibility problem between Windows* 7 and in the Quartus® Prime Standard Edition software version 18.0, you may not be able to paste symbols in a Block Symbol File.
Resolution
To work around this problem, follow the next steps:
1. Select the symbol to be copied doing a left click on it
2. Hold down the control key while dragging the symbol to the desire location
3. Release left mouse button and then the control key