There have often been requests for how to use a Report Index/BOM Item number that is automatically assigned from a Repeat Region / BOM table. This parameter is rpt.index.
There are two problems. One is that the table uses a calculated output. The value does not exist until the table exists. The other is that multiple tables can exist in a single drawing and the various tables can have different values for the same component. To get the correct index number one would need a reference like:
index(table_ID, component_ID)
To avoid that one needs to define the index number independent of the existence of a table; I mentioned this in regards to Simplifled Reps. One method is https://community.ptc.com/t5/Creo-Modeling-Questions/Create-a-BOM-index-between-Simplified-reps/td-p/62383/highlight/true/page/2, 08-03-2017 04:30 AM.
I understand that a facility to pre-assign item numbers is coming via Windchill, but I've experienced organizations which assign multiple item numbers to the same item; my method works for those while the Windchill method will not.
