Index for non-alphabetec characters

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In my settings I defined an index which starts with "#", which sorts artists with non-alphabetic characters at the start.
There are a few artists where I would like to change this whitout the need to change the folders or the artist-tags.

i.e. artists like
'Sonny Boy' Williamson (should be sorted to "S")
...And You Will Know Us By the Trail of Dead (should be sorted to "A")

So far I found no solution to achieve this.
Adding ' or ... to the words to be ignored in the settings does not work.

Any hints?