Quick Answer: This feature is not available today because of a lack of support of multi-channel MIDI applications by regular plug-in technology.
Deep integration of Liquid Notes into the DAWLiquid Notes is a powerful tool for fast editing of harmony and melody in MIDI arrangements. Compared to standard third-party MIDI manipulation software communicating with sequencers, Liquid Notes is a multi-channel MIDI device: i.e. for a precise harmonic analysis, it needs to access every note on every instrumental track of a song. Consequently, it can only function on complete arrangements.
Regular plug-in technology doesn't support the latter, as they only operate on a single track. This is a serious technical limitation, which renders the use of Liquid Notes useless.
This is why today we cannot offer a deep integration into the DAW, as you are used to it from other applications. In the meanwhile, we have created Liquid Notes for Live which offers quasi-plug-in features in Ableton Live 9 and are pushing for a solution with DAW manufacturers.
Read more on the technical discussion in this article - http://www.re-compose.com/differences-between-liquid-notes-products-and-plugin-standards-explained.html.