!!!Development stopped!!!
Sorry everyone, but I abandoned Firefox for Chrome.
Here is why.

Features

• Display bookmarks results on the search engine page
• Options of filtering: excluding or including URLs, subdomains, domains or tab
• Add-on button allowing above options on current web page
• Default search engines:google, stackoverflow, dogpile, baidu, yahoo, bing, ask, ecosia
• Shows viewpane as icon until searchbox contains > 2 characters
• Search bookmarks for same keywords in url and title
• When all keywords not found, search for one less keyword combination (marked with different icon)
• Search bookmarks for exact matching urls from search engine results and highlight them
• Clicking on "Found" shortly highlights them even more
• When bookmark url matches below scrolling, show a jump button at bottom
• Mark keywords in different colors (optional)
• •Show only small window with icons (minimize)

Future features when Firefox API "bookmarks" are good like before again

• Show bookmark favicon
• Search bookmark tags You can help by voting for this: https://bugzilla.mozilla.org/show_bug.cgi?id=1225916
• Search bookmark description
• Open Bookmarks Sidebar when clicking bookmarks
• Open edit dialog to edit bookmark
• Search similar (=not exact) urls

Install

• License: BSD 2-Clause "Simplified" License
• Weekly downloads: 1
• Average daily users: 5
• Rating: 4/5 of 5 ratings
• Created: 2018-01-06 17:13:11
• Last updated: 2020-02-14 14:00:15
• Homepage: https://github.com/e-motiv/Webextension-Bookmarks-in-search-engines
• Support site and email
• Orig: https://addons.mozilla.org/en-US/firefox/addon/bookmarks-in-search-engines/
• API: BookMarksISE@e-motiv.net