In OS X, clicking on a dock icon shows all open windows for the app. In Ubuntu, clicking on a launcher icon only shows the most recently used open window. This is annoying if you want to copy files between two folders or view all Xpad note windows.

Ubuntu 18.04

In Terminal
sudo apt install dconf-tools
dconf-editor
org / gnome / shell / extensions / dash-to-dock
Change click-action custom value to minimize
Another change to match 16.04 functionality when scrolling over app icon:
Change scroll-action custom value to cycle-windows

For Ubuntu 16.04 read on.
Continue reading Tweaking Ubuntu Unity To Show All Of An Apps Windows →