When looking at the Line ID on a transaction saved search I seem to get IDs like this: What is taking up ID 2 & 3 for example?

Could be some combination of: 1. Shipping Line 2. Tax Line 3. 2 & 3 were deleted. NS doesn't re-use line IDs if lines are deleted

you can also look at unique line id if that helps

And Line Sequence Number

I excluded Shipping Line, Tax Line, COGS line & set the Main Line to be false. So I guess it makes sense to then have the Line IDs to be in a different order.