I don’t think there is a built-in way of doing this, but you could try hiding topic list items from a specific category with CSS using something like this (replacing x with the category “slug” from category settings):
.topic-list tr.category-x {
display: none;
}
However, this would make them disappear from any topic list, meaning to topic list for that category would just be blank! So remedy this, we could exclude the code CSS from affecting the category page like this:
body:not(.category-x) .topic-list tr.category-x {
display: none;
}
If you also want them to show up when the users search for a particular tag, you could add that as well:
body:not(.category-x):not(.tags-page) .topic-list tr.category-x {
display: none;
}
This would probably require a custom component. There might be an existing Customization > Theme component that could do something like that, but I can’t think of one off the top of my head!