in logback-ecs-encoder/src/main/java/co/elastic/logging/logback/EcsEncoder.java [161:168]
private void serializeMarkers(ILoggingEvent event, StringBuilder builder) {
Marker marker = event.getMarker();
if (includeMarkers && marker != null) {
EcsJsonSerializer.serializeTagStart(builder);
serializeMarker(builder, marker);
EcsJsonSerializer.serializeTagEnd(builder);
}
}