Feature request: index value formatting

[ruckmann]

Hi Simon,

I am still on the way to restructure my music collection using the new indexValue functionality. Just discovered the following limitation:
indexValue applicable to index tags only: No chance to format auxiliary tag (re-used as IndexValue format input, but not listed as index tag)

Of course, there is a simple workaround: Move needed tags to the index tag list. However, index tag list blows up with additional tags really useful for navigation purposes.

I would be happy, if you would see a chance to remove this limitation.
B.t.w. Extending the functionality would change its meaning from IndexFormat to a general TagFormat functionality (but still working differently to displayFormat). But, why not?

I am looking forward to hearing from you