Thank you for the answer.
I know. I clicked after add the custom search engine. But the problem is not the default custom search engine.
As I already stated in my post; the rest of them does not show up. Please refer to the picture 1-4. No matter which custom search engine choose as a default, the rest of the custom search engines not show up.
2nd problem; If the newly added custom search engine chosen as default, I cannot search from address bar. Writing the search term and press enter sometimes work sometimes not (especially not work after restarting MX6).Refer to the picture 5-6
* If I select and copy something from any website or from clipboard or enter manually (word, sentence....) (e.g. "cloud storage"), then "Paste and search for" option (right click to address bar) grayed out (although not working for new default custom search engine either). But if it is website address then it is working.
Writing search term in an address bar and hit enter do not work. But if it is a website address then it is working as it shoal be (e.g. "https://en.wikipedia.org).Please refer to picture 7-10.
3rd problem: If I select a word or sentence in the web page and drag and drop, MX6 doesn't open new tab and search. If I Drag and drop to the address bar, MX6 does paste it to address bar but, hitting enter does nothing. Refer to picture 11
*But if, dragged and drooped item is a link, then MX6 opens the new tab and go to the address as it should be. Refer to picture 12.