Hi @willemdh,
You shouldn't run in to any issues running side-by-side with Windows Defender.
We've done everything we can to make sure that we do not conflict with Defender (Or any other security product that is using documented APIs properly). If you run in to an issue where Endpoint Security and Defender are not working well together or are otherwise negatively impacting user experience, please let us know so that it can be looked at and fixed.