Roboflow
Roboflow is sooo good to generate data and then do Transfer Learning. It is free for open-source datasets.
It automatically does the Train-Val-Test Split for you, and export into data formats that work for YOLO.
https://blog.roboflow.com/roboflow-command-line-interface-for-computer-vision/ Easiest way is to do it through the CLI
npm i -g roboflow-cli