Fred,thanks a lot for your help!
What you said just what I want!
You have described the method in detail.
I did it step by your instruction,but it does not work.
After restarting the browser,
the deled lines still exist at URL in the dropdown menu.
What's wrong with it?
BTW: I find the location of profile is in Edit/Preferences/Configs/Prefs.js
not in Edit/Preferences/General.