I recommend you to reread the use cases of Delete button in the manual. It's basically like that:
- If you see shape A + B are merged, only press Delete does not work! Instead:
-Navigate the game to a location when only A or B visible, let's say A is visible. Select A and change it to a different pattern then press Adjust. It will create a new pattern for A.
- Continue to navigate the game to a location when both A and B are visible. Select it and hit Delete. Then 3DNes will delete the A+B pattern, recognize A pattern and create a new pattern for B.
Hope it helps you in some situations.