I believe the logic is to insert new lines under the values that you've specified which is why, on the screens, you can't insert a line above the first line. Also why you can't insert unlimited records in between two existing rows.

So, if the first line on the order has a LINENO value of 32 then try populating that field with a value of 33 before saving.

Or just append and keep your hair.

yea, it seems like each new line is in increments of 32.  so line 1 = 32, line 2 = 64.  and then if you insert a line between, it halves the difference, so not Line1 =32, line 2=48, line 3=64

I guess it's assumed that you would never insert more than 31 more items in between original lines.  

Have you tried setting DETAILNUM instead of LINENO?  I believe that's what controls the order in which lines are displayed.

I have found and am going to try this, https://smist08.wordpress.com/2010/11/07/entering-orders-and-headerdetail-views/#comment-3642, which is basically browse to the record before your insertion point and then do the insert. If you want to insert at the beginning you need to "clear" the record and then do the insert.

I really wish there was better documentation about the view fields. LINENUM seems like it should work as does DETAILNUM.

Just as a followup, the method in the link that I posted works for both order and purchase orders.