Converting synth arpeggio's to MIDI notes

Not sure if you are only running audio in or have a midi in as well, so I can only think of one way at the moment
Take you audio (monophonic) file and dbl click to go into edit.
Select variaudio and then pitch & warp - this will show you your notation
Select “extract midi”, then destination = new midi track
Should be pretty close.
The manual has loads of info on this (that isn’t meant as a criticism by the way)

Neil B