Ubuntu 18 lts – custom setting

# use scroll to move between windows in dock
gsettings set org.gnome.shell.extensions.dash-to-dock scroll-action 'cycle-windows'

# separate / isolate apps between screens
gsettings set org.gnome.shell.extensions.dash-to-dock isolate-monitors true

other options when clicking on dock icon

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

'skip'
'minimize'
'launch'
'cycle-windows'
'minimize-or-overview'
'previews'
'quit'

you can list available options using

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