While you may not be able to bind Ctrl+Click to do what you want, you can make it such that clicking successively on the icon cycles through open instances. If your dash currently does not currently behave like that, then you can set it that way with the command:
gsettings set org.gnome.shell.extensions.dash-to-dock click-action 'cycle-windows'
While Ctrl+click will launch or switch to an application, it will not do extra actions (e.g., it will not cycle). To my knowledge, you cannot further customize Ctrl+Click behaviour.
However, you can further customize Shift+Click behaviour, and in addition middle-click and Shift + middleclick.
Use the gsettings range
command to query the possible values of the different keys controlling click behavour, i.e., click-action
, shift-click-action
, middle-click-action
and shift-middle-click-action
, for example:
gsettings range org.gnome.shell.extensions.dash-to-dock click-action
Then use a gsettings set
command (see first command for an example) as above to set one of the available values. Use a gsettings reset
command to reset the value to the default value of Ubuntu, for example
gsettings reset org.gnome.shell.extensions.dash-to-dock click-action