Dear Su Myat,
Good day! Thank you for posting to Microsoft Community. We are happy to help you.
From your description It seems Metadata Columns in SharePoint list Can't hide behavior from your side.
apologized situation you encountered, we do understand the inconvenience caused and apologize for it.
I read your query carefully couple of times and I do some test I am able to hide the columns by bellow method
About "hide column", if you don't want users to see it no matter in the list page or when creating new items, you can do it in this method.
1) click "add column" and click "show or hide column", untick the column you doesn't want to display and save it.
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- click "New" to create a new item. In the right side pane, click "edit" icon >> edit columns >> untick the columns you don't want users to see when creating new item, save it.
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Your understanding and patience will be highly appreciated.
If there is any misunderstanding, please feel free to correct me.
Have a nice day!
Best regards,