ユーザーが自分のスレッドのみを表示できるカテゴリはありますか?

I’m not sure I understand your use case

If the users themselves are the only ones who can see it, how does this create support?

If they want to send a message to staff for support, then they can use the PM functionality and send their request to the Staff group (or whatever support inbox is created on the site).

Can you elaborate on how this would be used?