I don’t think Aux configs are supported, but you can specify which button to bind to a wheel menu, which is what most Aux configs are for. There are also functions for button remapping and multi-action buttons (eg activated by trigger depth).
Most other functions typically used for Aux configs like skydiving, driving etc that can cause problems when using m/kb on APEX are handled via the game’s controller actions and aren’t really needed on NEXUS.