UR28, Rev-x and Cubase 7

What is, and how do we access the custom pane? As mentioned below - I’m having difficulty figuring out how to use the UR28 rev-x and sweet spot with Cubase 7

Currently REV-X is not accessible from the input channels. As a workaround please open REV-X via the custom pane. In addition, it is not possible to save and load presets for REV-X.