Any time you make a change to an arpeggio, the data is saved as soon as you leave the Arp menu where all the parameters are located. If you don't want to overwrite the factory Preset, it is recommended that you first copy the desired arpeggio to a User location. This can be done in the Save menu, see page 229 in the manual. Once you have copied it, make sure you select the new location you saved to for your Preset in the Preset edit screen, so that your Preset will use the new Arpeggio you're making, not the factory one you copied from. Once that's done, resave your Preset before you forget, then turn ON the Master Arpeggiator in the Arp Menu. Next select the user location where you saved the Arp you want to edit. Once it is selected, you can change any of the parameters you desire and listen to the results as you play back your Pattern, or hold a note. Once you are done editing, simply leave the Arp menu and the settings are saved automatically.