“An 11,000 year old engraved shale pendant discovered by archaeologists during excavations at the Early Mesolithic site at Star Carr in North Yorkshire.”

Given that the scientists have shown it was done in stages it’s clearly not a whole design like a tree or leaf. It represents a process, which is most likely to be related to hunting/foraging in a landscape. It looks to me like a map of a local river and its tributaries – plus notches to record hunting/foraging trips in the marshy fringes of that river and their relative success. Perhaps the owner might have had a collection of such pendants, to serve as guides to navigation and hunting along a river at different times of the year.