RoundCube 1.5.2 on CentOS 8 - Cannot see Threading Option

[vaisam]

I have installed RoundCube 1.5.2 on CentOS 8.
Skin: Elastic
IMAP Email Server: Gmail

Somehow I'm not able to find the Threading option.
I have checked all the options in the UI.

Someone, please help me out.

Thanks