Filter effect: owner's manual

Filter effect: applications

Axe-Fx II firmware 15: "Added Variable-Q EQ types to Graphic EQ, Filter and Amp blocks. Many “classic” graphic equalizers use variable-Q designs which may be more familiar to some users as opposed to constant-Q filters. In the Filter block this type is selected by choosing the “Peaking2” type. The Graphic EQ block now has four constant-Q modes and four variable-Q modes. The Amp block now has three constant-Q modes and three variable-Q modes."

Axe-Fx II firmware 15.04: "Added “Lowshelf 2” and “Highshelf 2” EQ types to Filter and Parametric EQ blocks (in the Parametric EQ block these are referred to as “Shelving 2” types). These types recreate the analog shelving filters found on classic mixing consoles. These filters are somewhat quirky and exhibit “overshoot” which gives them a certain musical quality. Set the Q between 0.5 and 0.707 to recreate those classic sounds or experiment with the Q for different amounts of overshoot. These filter types are great for getting that massive sound associated with passive equalization."

The Tilt EQ is a slope filter that allows broad adjustment of the tone using just two parameters: Frequency and Gain. The Gain parameter sets the maximum gain of the filter relative to the center frequency. For example, a gain of 10 dB would set the maximum gain to 10 dB. The gain at the center frequency would be 0 dB and the minimum gain would be -10 dB, therefore a total of 20 dB of EQ would be applied.

There's no dedicated Envelope filter effect block. You can achieve this effect by attaching a LFO or Envelope to a Filter (or Wah) block.
You'll find examples in this thread, this thread and on Axe-Change. Or try the Psychadelic Duck preset.