Is combinining more than one gsettings options for click-action on Ubuntu dock possible?

Update: On newer versions of Ubuntu dock, this feature can be turned on by simply running the following command in Terminal:

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

Original answer:

No, it's not possible (yet). Dash to Dock developers did implement a 'minimize-or-previews' action in version 63, but this version is not available in the official site yet and Ubuntu dock being a fork of Dash to Dock also doesn't support the action yet.

But you can set one action to mouse click and another to Shift+mouse-click as an alternative. For example, run

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

to set 'minimize' action to mouse-click. Then run

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

to set 'previews' action to Shift+mouse-click.