Went to an official Montage workshop in Germany put on by Yamaha.

The 256 User Arps were mentioned several times in the presentation so I asked if there would be some software tool made available for editing them and the reply was that Yamaha was "probably" going to have something.

I wonder if this was just pure speculation.

Seems strange to me to promote User Arps and the only way to edit or create them is via a Motif XF.