If I idle my car overnight will it damage the engine in any way?

Hello,

If this is just done for one night, then it should be ok. However, you do not want to do it all the time, as it can have long-term damage to the engine.
A cars engine is not designed to run at a given rpm for a long period of time.
As you know typically an engine only runs for a few hours, then it is allowed to cool down.

If you were to run an engine constantly for an extended period of time at a contact speed, there will be certain wear on the internals as there is no time to cool down. This can have a long-term impact on the engine's health.

So really the short answer is no it will be ok to idle overnight. But you do not want to do it frequently.

Please let me know if you have any questions.
Thank you.

https://www.2carpros.com/articles/how-a-car-engine-works