Althought the FAQ claims, it is not possible, there is a way to use custom application icons in xfwm and e.g. the panel icon box wich Xfce.

In Debian Etch, I added the file /etc/X11/Xresources/zz_MyXresources with the line

XTerm*iconPixmap:       /usr/local/X11/bitmaps/sh_32x32.xbm

And created sh_32x32.xbm in /usr/local/X11/bitmaps/ to have everythint set up automatically everytime I log in. If you can't or don't want to fiddle arround with files system directories, putting the line into the file ~/.Xresources might do as well.

Credits: I found the key hint here (Gone, see here for an archived version).

Try wmctrl

Credits: I found the key hint here and here.

There's a toggle in the Mouse & Touchpad Settings, which did not show up for me. It turned out, a binary called syndaemon was missing. A simple

apt install xserver-xorg-input-synaptics

did cure the problem. Alas, the toggle showed up only after a reboot - a systemctl restart display-manager would have probably been sufficient.

Credits:

• Xfce4 manual
• Ubuntu package search

X11 Xfce