In my side menu, I have this structure:

Home
Discussion
|- Topic 1
|- Topic 2
|- Topic ...
|- Topic N
About us

where Topic 1...N are sub-menu under "Discussion" and links to different pages. The item "Discussion" is just to represent the structure, it doesn't link to any page.

Now I can make the "Discussion" not link to any page by setting empty URL. However, user can click "Discussion" to collapse/expand the Topics 1...N items under "Discussion"

What I want is to disable such collapse/expand function for "Discussion" so that

1. "Discussion" appears just as a static header text, and unclickable at all (even no hover color change effect)
2. The subitems Topic 1..N is always displayed
3. When user click "Discussion", it won't collapse the Topics 1..N items.

Any advise on how to do it?