Thanks for this. I've been concerned about QuickSearch disappearing, and this seems to solve it.
I didn't see it in the notes, but if you've already set up QuickSearch, you can simply copy and paste the bookmarks from the Quick Search folder to the Searches folder, and everything seems to work.
With QuickSearch, if you right-clicked with nothing selected, it checked for text in the paste buffer and, if found, offered to search for that text. It's pretty handy, and it would be nice if you could add that.

I like the suggestion by Teko for a "current site search" option for Google, but understand what you say about it deviating from what the add-on does. But what about this approach, which generalises the idea and might fit in a bit more naturally. Currently, the web address has %s replaced by the text selection. What if also %d (say) was replaced by the current domain name. The user could then manually edit the web addresses exactly as they like, for any search engines of their choice. For example, for a Google site search they'd change "%s" to "site:%d %s". This concept could be extended to %u (say) being replaced by the URL. It could then be used to send the whole page to Google Translate, HTML validation services etc. (In this case, the add-on would also need to work with the Context Menu you get when there's no text selection). I realise that it's a bit more work for the user to set up initially, and that there might be technical reasons why it's not suitable - but I thought I'd put the idea forwards.

Good work but how come there are pages e.g. like http://www.thai-language.com/dict/search that is not working?

The setting "When you do a search..." is not saved after you close FF.

Thanks for the hard work, it works very well.
just one suggestion: would you add an option/entry for searching the current site using google (Site Search)?

Have to create a bookmark folder first, and then restart FF, really? Better use the web-extension called "contextual-search".
https://addons.mozilla.org/en-US/firefox/addon/contextual-search/reviews/

Works fine as described. Formerly I used https://addons.mozilla.org/de/firefox/addon/context-search-x/ which is a legacy add-on, but two of its features I wish for "Context Search WebExtension" too:
1. Favicons
2. The uppermost search engine is dedicated as standard. Therefore no need to move the mouse into the pull down menu of various search engines, but click just the main entry "Context Search" (with the magnifier icon) in the context menu and - voilá - the standard search engine is chosen and searching.
3. Of course, grouping would be a nice-to-have feature too for me.

Great job. I was looking for this since no other addon is a webextension. Just one question though, but let's take it to the support page:

https://github.com/NumeriusNegidius/Context-Search/issues/1

combo from 2 legacy add on add to search bar and context search (legacy)

This addon works great. I was hoping that some kind developer would make this extension for WE. A great big thank you for making the transition to WE much easier. I use the ability to search stores and anywhere else I wish several times a day.