Order of BOM balloons & items in table

There is a way to do this with component parameters.  See https://www.ptc.com/en/support/article?n=CS197902

After reading your question again I think it might be better to use a 'normal' parameter instead of component parameters.  This would let you set it one time and then display the same value everywhere it's used in any assembly (assuming your repeat region table is set up correctly.)  You would just have to make sure you never reused this same number in any other model or you could end up with duplicate numbers in the same table.

This is generally considered a bad idea.

Your example is with a high number, but what about lower numbers, like 1-100?

The 1/4-20X.75 HHCS is to always be item 96?

That would use a lot of numbers if you used a fixed line item for every part.

I have over 2 million parts in Windchill and 11K+ in hardware family tables.

Here's how to do this:

1. Go into Repeat Region Relations. Add the following relation:

pos = rpt_index
if exists("asm_mbr_position") == true
pos = asm_mbr_position
endif

This will create a new parameter called "pos", assign it the index value, then, if the part has a parameter called "position", set the "pos" value to that instead.

2. Add a new column to your Repeat Region. This column should hold display the parameter "&rpt.rel.pos". This is in ADDITION to the "index" column. The problem is that for some reason Creo doesn't create the index unless it's displayed in the Repeat Region. So if you remove that column, your relation is going to fail, since it can't find the "rpt_index" parameter. To avoid this, remove the header of that column, set the text size of the entire column to 0.0001, and likewise set the column width to 0.0001. The column should now be pretty much invisible.

3. Select the table (make sure to select the entire table) and Edit Definition/Properties (depending on your version). Set the BOM ballons to display your rpt.rel.pos, instead of rpt.index.

Now you have a repeat region which will use your Position parameter if it exists, and just use a normal index if it doesn't. Note that it doesn't ensure there's no overlap, so if you have enough parts, you could get two parts with the same index this way. There's no simple way to avoid this (there might be a complex way), so I'd recommend to just keep the fixed position numbers high enough that it won't happen.