I don't know if it works with the track number field as I have not tried it but when setting up a collection of items that I intend to add to later I use an index field and leave gaps in my numbering system.
For example the original list has numbers 1000, 2000, 3000....
I can add extra items between them as 500, 1500, etc.
This can stand quite a lot of future additions!
Eventually you might need to renumber everything and start again.