[Simon Lloyd]

This thread will help you https://vborg.vbsupport.ru/showthread.php?t=215032 the actual condition you are looking for is

<if condition="!in_array($forum['forumid'], array(1,2,3,6))">DO SOMETHING</if>

notice the ! which makes this statement read:
if NOT in this array of forumid's then DO SOMETHING.

If you use it like this

<if condition="in_array($forum['forumid'], array(1,2,3,6))">DO SOMETHING</if>

Then unless the forumid is the same as one of those in the array then DO SOMETHING will NOT show