You can use OnSong's Timeline feature to record a timeline "map" of a song. You can use Timeline to add a "Toggle" or "Start" autoscroll action manually in timeline which will start linear autoscroll at that point, and you can also manually add events to the timeline at specific time codes such as MIDI.
To do these things, open the Autoscroll Menu by tapping and holding on the Autoscroll Button in the Live Bar and then Choose the Timeline tab . Tap on the Edit button to enter Edit Mode . Next, tap on the + button to choose an action to perform using the Action Picker . Choose the action. When you're done, you can use Edit Timeline Event which gives you the ability to change parameters of the event as well as its timecode.