[fulmicoton]

Not yet. Only prefixes. Also you could probably cook something with an ngram tokenizer.

Is it for a field with a high cardinality? If you tell us more about your use case, maybe we can find a workaround.

[marsupialtail_2]

No just curious. I understand how your indexing structure based on SSTables could find it challenging to support substring search in general. I think it tradeoff between fast querying and flexible functionality