No, it is not possible to use second or third or fourth party plugins. The ones which you see are so-called Fat Channel plugins, which are variations of equalizers and compressors. Basically the Fat Channel uses a "standard" 4-band/6-band parametric equalizer, compressor and limiter. Limiter plugins are also conceivable, but who would need something else as the built-in "standard" limiter? The Fat Channel is part of the firmware. Also part of the firmware are the reverbs, delays, chorus and flanger. The PreSonus mixers can use what is especially made for them, their firmware and their technical construction. All digital mixers do it this way. If you want to involve external plugins, you need a DAW connected to your mixer or the coming AVB Soundgrid Bridge from Waves, allowing you to use Waves plugins,
