Hi and welcome to Arturia forums.
FYI: You have posted in a Analog Lab legacy forum. There is a separate forum for the current version.
The preset Applied is using SEMs 8 voice programmer. It's not an arpeggio but a sequence where note intervals is programmed for each step.
You need the full application to change anything in the 8 voice programmer and for an arpeggio. You can't do it, if you only have Analog Lab.
The sequence is going forward but chnage intervals both up and down. It's not set to retrigger on key down. That might be why you experience it's random, as it's possible, that it start on different steps of the sequence, depending on what you do, when you use the preset.