I know people find Writer frustrating, and now I know why?

I just want to create a simple quoting solution which uses data in Bigin, simple you would think. The best way seems to be Merge in writer. Can get all the standard fields in and working fine but I need to have in there a product, QTY, price field from Bigin products. I can see those fields, but as soon as I add it says they need to be in a repeating, but when I try to add them in a repeating, they are then greyed out!

Pulling my hair out here, so frustrating!

Any help or ideas?