I tried to add boosts on an @IndexedEmbedded Property:

@IndexedEmbedded(includePaths = { "name" })
@Boost(0.7f)
private TestEntity entity;

The Boost annotation gets read in AbstractDocumentBuilder.checkForIndexEmbedded and is stored in the PropertiesMetadata.embeddedPropertiesMetadata, but the extracted value isn't used for the calculation in DocumentBuilderIndexedEntity.buildDocumentFields. A TODO is stated in the method part, where the embedded objects are recursively processed:

//TODO handle boost at embedded level: already stored in propertiesMedatada.boost