FYI, I have stopped relying on the app, since it doesn't appear to work consistently. I've found that after clearing non-favorite cookies and databases, then closing preferences, then reopening preferences, the cookies reappear. Also, I've noticed that after clearing cookies, I can switch to the Privacy tab of Safari preferences and see that many non-favorite cookies remain. It's clearly not doing what it should be doing. Here are a few screen caps to illustrate:
1. Privacy tab before clearing
2. Cookies tab before clearing
3. Cookies tab after clearing
4. Privacy tab after clearing