How to install & use this extension

Recoll Search Provider integrates the recoll full-text search results into GNOME Shell.

As long as this extension is not listed on the official GNOME Extensions platform extensions.gnome.org, you can manually install it:

Create a new folder named recoll-search-provider@sebastian.leidig.gmail.com in the folder ~/.local/share/gnome-shell/extensions
Download the full code with all files into this folder
Enable this GNOME Shell Extension ("Recoll search provider") in GNOME Tweaks or however you manage your GNOME Extensions.

More Information

This extension is based on the GNOME Shell "Sample Search Provider" project. To build your own search providers, have a look there.