As mentioned above, you could use templating to create a template, however that can be quite advanced, so if you are instead asking for a simpler way to add a “Generic HVAC” as a virtual HVAC device via the UI then check out this this idea of adding more “generic” integrations built-into Home Assistant so would not need to build templates yourself → WTH not add more native "generic" integrations built-into Home Assistant core to create virtual devices (like Generic Thermostat, Generic Hygrostat, and Generic Camera)?