Currently, flattened type cannot be a dimension. This limitation restricts us from effectively utilizing flattened fields within TSDB enabled data streams. The point of this is enhancing the existing functionality by allowing the declaration of multiple values as dimensions, even when they are flattened.

- name: dimensions type: flattened dimensions: ["a", "a.b", "c.d"]

Support for flattened multiple dimensions was added in ES in 8.8 elastic/elasticsearch#94842