Hi @Trang Le
I suggest you post a new thread on following forum check whether there is any workaround.
The reason why we recommend posting appropriately is you will get the most qualified pool of respondents, and other partners who read the forums regularly can either share their knowledge or learn from your interaction with us. Thank you for your understanding.
Besides, based on my tests, there is character limitation for column header in Power Query. As following image shown, if the character length is 263, then there will be a prompt when I create a query, that the header will be truncated.
If the character length of the header is less than 255, the header will not be truncated when unpivoting data.
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