sudo add-apt-repository universe
sudo apt install gnome-tweak-tool
Use activities and search for tweak keyword to start the Tweak Tool. Alternatively, execute the bellow command:
gnome-tweaks
You may now install additional extensions to further tweak your system. Search for available gnome shell extensions:
apt search gnome-shell-extension
sudo apt install gnome-shell-extension-gsconnect
Source: https://linuxconfig.org/how-to-install-tweak-tool-on-ubuntu-20-04-lts-focal-fossa-linux