Some aircraft belonging to ‘Airliners’ are to find in ‘others’ in the content manager. That should be corrected (Synaptic A220 and Pilot’s Dash 7).
Not sure if the issue is on the sim side or on the developers side that may need to send their package with a specific “Airliners” tag to be correctly classified in the content manager ?.
You may want to report the issue to those addons developers.