Hopefully, this information isn't redundant and posted elsewhere. I wasn't able to locate this information in either the Helix manual or the HX Stomp manual. To the contrary, both manuals list CC71 as "reserved for future use". However, I have found that these commands do work on Helix Floor and I assume they may work on Helix Rack, and HX Stomp.
Footswitch Mode - Stomp - CC71 - Value 0
Footswitch Mode - Preset - CC71 - Value 1
Footswitch Mode - Stomp Edit - CC71 - Value