Add docs on indexing for filter column

[bernt-matthias]

Wondering if it would be a good idea to push name based adressing of columns more by rewriting the examples a bit, but most of them (or all) seem to be rather abstract, i.e. there are no real datatables that they refer to (so I do not know the names of the columns).

xref galaxyproject/tools-iuc#6337

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• This is a refactoring of components with existing test coverage.
• Instructions for manual testing are as follows:
  1. [add testing steps and prerequisites here if you didn't write automated tests covering all your changes]

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[github-actions]

This PR was merged without a "kind/" label, please correct.