Hi, Luther, I've brought back touchpad tapping with such config. Need to use gdm-service-type instead of slim-service-type   
 (services (cons*
 (service xfce-desktop-service-type)
 (service dhcp-client-service-type)

 (modify-services 
 (remove (lambda (service)
 (member (service-kind service)
 (list ntp-service-type avahi-service-type
 bluetooth-service network-manager-service-type)))
 %desktop-services) ;end of remove lambda services

 (wpa-supplicant-service-type config =>
 (wpa-supplicant-configuration
 (interface "wlp2s0")
 (config-file "/etc/wpa_supplicant/wpa_supplicant.conf")))

 (gdm-service-type config =>
 (gdm-configuration
 (xorg-configuration
 (xorg-configuration
 (extra-config 
 '("Section "InputClass"
 Identifier "touchpad"
 Driver "libinput"
 MatchIsTouchpad "on"
 Option "Tapping" "on"
 EndSection")
 )))))  
Apr 4, 2019, 7:49 PM by lutheroto@gmail.com: On Thu, 4 Apr 2019 20:47:04 +0200 (CEST) <znavko@tutanota.com (mailto:znavko@tutanota.com)> wrote:  Sorry, my tapping config that I've gave is not working too with current commit. Need to use manual or maybe it is a bug.   If it's not a Guix bug, then the problem is probably with the string that we pass to extra-config. The documentation for that is at xorg.conf[0] and libinput[1]. If that's not what the problem is, I have no idea what to search for in the Guix manual.  [0] https://www.x.org/releases/X11R7.7/doc/man/man5/xorg.conf.5.xhtml (https://www.x.org/releases/X11R7.7/doc/man/man5/xorg.conf.5.xhtml)  [1] https://www.mankier.com/4/libinput (https://www.mankier.com/4/libinput)  Luther