The Recoll source tree contains the source code to the recoll_applet, a small application derived from the find_applet. This can be used to add a small Recoll launcher to the KDE panel.
The applet is not automatically built with the main Recoll programs. To build it, you need to unpack the Recoll source code, then go to the kde/recoll_applet/ directory, and type the usual configure;make;make install.
You can then add the applet to the panel by right-clicking the panel and choosing the Add applet entry.
The recoll_applet has a small text window where you can type a Recoll query (in query language form), and an icon which can be used to restrict the search to certain types of files.