Repeat regions - unfix index that is not shown in a table

Hi all,

I'm struggling to find a solution to an apparently simple problem. I have a repeat region listing parts, whose indexes have been "fixed" to remain always #1 , #2 and #3 (in the desired order).

Now, component #2 has been replaced with another part (different part number) and so the BoM table is now listing items #1 and #3 (associated to the same p/n as before), leaving a gap inbetween; the new item, which replaces #2 is now listed as #4 because it's the first available index.

I thought I could simply fix index for the item which is now #4 and assign #2, but I get an error because index #2 is already assigned! But I can't unfix it, because it's not possible to select it (its row in the table does not exist anymore). Does anybody know how to work this around, without deleting and recreating the table? Thanks.

(I simplified the example on purpose, but this scenario might apply also to assemblies with 100+ parts, where recreating the table from scratch is not an option)