Changing GTK Theme for Ubuntu 18.10
You are Welcome! The Tutorial Shows You Step-by-Step How to Install Change GTK Theme in Ubuntu 18.10 Cosmic GNU/Linux.
And GNOME Tweaks (formerly known as GNOME Tweak Tool) allows adjusting several advanced GNOME options that can’t be configured in the official GNOME Settings app.
1. Installing Gnome Tweaks
Install Gnome Tweaks Tool to Switch ThemeInstalling Gnome Tweaks
2. Launching Tweaks Tool
Then Launch Tweaks Tool
3. Switching of Theme
Finally, Switch of Theme
So Now I’m truly Happy if My Guide could Help You to Change GTK Theme on Ubuntu 18.10 Cosmic!