Hi @Lukas Rieder I'm glad that you were able to resolve your issue and thank you for sharing your solution so that others experiencing the same thing can easily reference this! I am reposting your solution in case you'd like to accept the answer.
Issue:
Could not access the nested JSON data from the telemetry and display it on the IoT central variables.
Solution:
A quick fix for small device numbers (because it requires a lot of individual typing for each sensor in the UI) is to use mapped aliases, thereby extracting the elements from the JSON objects. This will extract those aliases in the telemetry data directly without putting them in nested objects. It allows to access these variables directly with a device template.
Then those variables appear in the telementry "top layer". which can be renamed with the device template and used for creating plots.
If I missed anything please let me know and I'd be happy to add it to my answer, or feel free to comment below with any additional information.
I hope this helps!
If you have any other questions, please let me know. Thank you again for your time and patience throughout this issue.