This point was not immediately clear to me.
After an automation plugin is added, you can find it in OF preferences --> automation section --> Configure Plug-Ins.
Keyboard based activation
When tapping a plugin for the Plugin Details, the specific action can be tapped, after which a new screen opens to define a keyboard shortcut.
These shortcuts seem to be dependent on the use of modifier keys (not part fo the standard on screen iOS keyboard). So these keyboard shortcuts are dependent on having an external keyboard attached (?).
Non keyboard based activation
The installed OF Automations are also available in the Share menu, when the shared input matches the input required for that specific OF Automation.