As title says, the metadata speicifier ShowOnlyInnerProperties doesn’t get applied to structs inside structs (simply does nothing).
Hello FelixHeimInreal,
Thank you for reporting this issue. This had been reported previously but unfortunately was not deemed to be a priority as it doesn’t block workflow. You can find the issue here. As it’s not a high priority, we will likely not be spending the time to fix it. If you do have an idea of how to fix it in Source however, please feel free to submit a Pull Request on Github and we will review it.