User Agent: Mozilla/5.0 (X11; Ubuntu; Linux i686; rv:15.0) Gecko/20100101 Firefox/15.0.1 Build ID: 20120907231835 Steps to reproduce: I deleted Google.com from my search engines in the "Manage search engines..." window to try and replace it by Google.com.au. Actual results: I noticed that I wasn't able to add Google to my search engines again, that the option didn't appear in the drop-down menu when I was visiting Google.com ou Google.com.au. Expected results: It should be possible to delete a search engine from the list and have the possibility to add it again if we change our mind or if our needs change. It is very confusing to see the option disappear, the user won't understand why. I tried this with several other websites (Bing, Ebay for example), it is not a problem only with Google.

Left click on the Icon of the search bar, selecting "manage search Engines" and "restore defaults" doesn't restore the default search Engines ?

It is true that "Restore defaults" brings them all back, I hadn't tried before because I thought it would replace the ones that were manually added. I still think that it should be possible to see the option "Add "xxx"" in the dropdown menu, even for the defaults.