What is "Custom Attribute Key Configuration" for ?
I'm trying to find any documentation or explanation about this interface from the internet. Unfortunately, I can't find any. Does anyone can provide a guidance or any document linkage? Thank you,

I'm trying to find any documentation or explanation about this interface from the internet. Unfortunately, I can't find any. Does anyone can provide a guidance or any document linkage? Thank you,

Hi @moses_maxen, thank you for the clarification. These two statements help me a lot to know the logic behind them.
One more question is about the setting process. I found no value from the dropdown field (the red rectangle below). Is any missing step while creating a custom attribute key?

Hi @practitioner-pin, I'm glad the clarification on the profile.XXX vs user.XXX was helpful. If the dropdown highlighted in your screenshot is empty, then it is likely that you have not yet passed in any profile parameters or created any profile scripts, that is what will be populated in that dropdown.
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