I just finished a new tool, compton-conf, for lxde-qt.
It's a GUI configuration tool for X composite manager compton.

Before using this, compton needs to be running with dbus support.
> compton --dbus

Then, we can edit the options of compton with compton-conf and apply them on-the-fly.
Before the world if full of wayland stuff, X11 and openbox will live for quite a while. So we have a composite manager.
Existing options are xcompmgr, xcompmgr-dana, and compton.
Of the three compton is the most actively developed and it added many new features to the forked xcompmgr code, including a dbus interface.
I'd suggest that we can launch compton by default in our desktop session. Or, alternatively, turn it off by default and provide an option in lxqt-config to turn it on.
Please try the config tool.