The simplest way (not necessarily the best if you have a huge amount of states to save, but for arguments sake we’ll assume it’s a simple setup with only a few doors) is to simply assign an integer variable to your door to give it an index, and a boolean variable for whether the door is closed or open.
In your save game if you have an array of door open bools then when the door is spawned you can load your array from the save and get the value from the array by the doors index.
You just have to make sure that every time the doors is opened or closed and the state of the IsDoorClosed? bool is changed you save the updated value to the array on that index.
Sorry if that’s not exactly what you were after but feel free to clarify if you need more specifics.