Thank you so much Magus069. I'm missing something still. Here is a screen shot of my form -- the actual names of the objects are different than what I typed above because they're so long I abbreviated them in my original post. I did change the code to match the names.
I tried inserting the full "name" of the repeat row instead of the 'Descriptiontable._descriptiontablerepeatrow' but that didn't work. I tried adding another parent. I tried making it just one parent.
to insert a row under the current row, you must specify at which index you want to insert the row.
so the insert instance should look like the following :
you might need 1 or two parent (you must use as many parents as it needs to reach descriptiontablerepeatrow starting at the add button) if the add button is a cell you will need 1 parent, and if the add button is inside a subform (which the subform is in this case the cell) you will need to use 2 parent