The Lubuntu manual says that [Super]+[E] is supposed to launch PCmanFM-qt, the default file manager for Lubuntu (for which I've just installed version 18.10). Reference: https://manual.lubuntu.me/2/2.4/2.4.4/pcmanfm-qt.html It doesn't. [Super]+[E] does nothing. The Global Actions Manager (Keyboard shortcut definitions GUI) will not allow anything to be assigned to [Super]+[E]. I found that keyboard shortcuts (aka keybindings) are stored in /home/ghw/.config/openbox/lxqt-rc.xml
<!-- Lubuntu specific : Keybindings -->
<!-- Keybindings for running applications on Home + E -->
<keybind key="W-e">
<action name="Execute">
<startupnotify>
<enabled>true</enabled>
<name>File manager</name>
</startupnotify>
<command>pcmanfm-qt</command>
</action>
</keybind>