Add option to hide duplicated index values (white font colour)

[foster999]

Is your feature request related to a problem? Please describe.
Some users are removing duplicated text in high level indexes - e.g. where it represents a super category.
This means that machine reading the data will require filling these forwards. If rows are reordered this data will be mangled.

Describe the solution you'd like
It would be better to keep this row-wise data in the table for machine reading, but instead improve human readability by making that text white.

[giro090]

I'm checking in with the presentation champions about this one :)