I do not recommend storing individual line numbers in the database. A fixed line number should only be used for selected events that you want to display in a specific position, out of the standard order. If you specify it for all events, it require a lot of manual work to maintain consistency of the Scheduler view.
See also:
https://code.daypilot.org/91222/javascript-scheduler-event-placement-strategies
If you want to apply custom order, I recommend using the event sorting feature that is described here:
https://doc.daypilot.org/scheduler/event-sorting/
The values used in the "sort" array will be used to arrange events in the specified order, while ensuring that they don't overlap.