This is one way of doing it.
Add this to the extra.less template - specify the node IDs, comma separated, as required;
Less:
[data-template="forum_list"]
{
.node--id
{
&2,
&4,
&8
{
display: none;
}
}
}
The node IDs can be obtained from the ACP --
admin.php?forums/main-forum.2/edit
-- or via the browser inspector:
View attachment 256487