FX Designer is a digital audio effect processor with a flexible signal processing design that allows to produce such audio effects as chorus, flanger, phaser, spatial effects, various reverbs and any combination of above.
The main idea behind the plugin is provide an easy way to create various delay based effects from the basic building blocks: comb and allpass filters. Many audio effects like phaser, chorus, flanger, reverb, delay are made by interconnecting these basic blocks into a network. For example chorus and flanger can be made by a series of parallel comb filters, phaser is a series of allpass filters and a basic reverb is a combination of 4 parallel comb filters followed by a series of two allpass filters.
But FX Designer is not just for creation of well-known effects that can be implemented standalone much better - it's designed to create new, unheard before effects. Take an example: With it it's possible to make a reverb that would sound like a room with sizes changing over time.
To create all that variety of the effects FX Designer offers 6 modulated delay lines with comb/allpass mode switch, 6 assignable LFOs and flexible tap signal router that allows to interconnect taps into a network. But you may not ever need to build your own network as the the plugin comes with 37 ready-to-use schemes that cover most of the useful effects.