How to change the behavior of clicking on grouped apps in launcher

Solution 1:

You can use gsettings to achieve your goal

If you run

gsettings get org.gnome.shell.extensions.dash-to-dock click-action

you should see different outputs for two different cases you mentioned, for example in the first scenario it should give minimize whereas in the second case it should be previews.

To set the preferred option as per the output of the command above, run

gsettings set org.gnome.shell.extensions.dash-to-dock click-action 'YOUR-PREFERRED-OPTION'

In particular, to achieve your goal, run

gsettings set org.gnome.shell.extensions.dash-to-dock click-action 'previews'

Solution 2:

You can user dconf editor GUI tool to update these changes easily

sudo apt-get update 
sudo apt-get install dconf-editor
dconf-editor