Kibana 6.2 introduced the ability for users to create custom visualizations using the open-source JSON-based declarative language Vega and its simpler version, Vega-Lite, allowing developers to draw visual elements based on multiple data sources without needing to develop their own plugins. This feature provides a blank canvas for developers, enabling the creation of complex visualizations such as Sankey diagrams and scatter plots, as demonstrated with examples using sample Logstash data. The process involves querying data through Elasticsearch and utilizing Vega code to design visual elements, including scatter plots that map data points based on time and bytes, and trend indicators that compare event counts over different time intervals. Through these tools, users can enhance their data visualizations in Kibana, making it easier to interpret complex data patterns and trends.