Sometimes we implement new features which could break the data stream / layout after updating. To avoid this and keep the backward compatibility promise, we've implemented the config flags.
Currently, no configuration flags available.
If you're updating from 2.x/3.x to 4.x please check out old configuration flags (https://github.com/dachcom-digital/pimcore-toolbox/blob/3.x/docs/70_ConfigurationFlags.md) first!