XF 1.5 How to display sub forum on index but not for all forums ?

[Sc0rps]

Hello dears,

i want to know if someone can help me to find a solution to display sub forums on index but not for all forums (i saw this xenforo forum who have it : (displaying on some forums)
https://realitygaming.fr

this will really help so thanks for you guys .

this is my site : https://virtual-gaming.fr