As you mentioned, this can currently be done via Shortcuts and Home but not from your application. Will be this feature added in future updates? I really want to make automatisation like was written in post above:
Open the Home app, and go to the Automation tab
Tap '+' to create a new automation
Tap 'A Sensor Detects Something', choose a sensor such as 'Motion', and hit 'Next' twice, to get the list of scenes and accessories
Scroll to the bottom of this page, and tap 'Convert To Shortcut'
Now that I'm in shortcuts, I do not have the option to choose any 3rd party Siri Shortcuts, only a smaller sub-set of options > I have bought the new iPad to make such automatisation an was very dissapointed, when in available Shortcuts in HomeAssistant was small list of Apps. 3rd party Siri Shortcuts are must have.