What is one recommended way of splitting Features into Stories during a PI Planning event?

One of the recommended ways of splitting Features into Stories during a PI Planning event is to use the horizontal slicing technique, which means implementing the simplest variant of the functionality first and then adding more complexity and variations as enhancements. This technique helps to deliver value incrementally, reduce risk, and enable fast feedback and learning. Horizontal slicing also supports the application of the Minimum Viable Product (MVP) and Minimum Marketable Feature (MMF) concepts, which aim to deliver the smallest amount of functionality that can provide value and validate assumptions. References: Exam Study Guide: SP (6.0) - SAFe® Practitioner, Feature, Story